NOVELTY - A reaction device (300) comprises: a reactor (200) to cause a reaction of a reactant; a first container (1) to house reactor; and a second container (2) to house first container, where a gas is injected to a space (13) between reactor and first container and first container is sealed, and an atmospheric pressure in a space (23) between first container and second container is lower than a normal atmospheric pressure.    USE - As a reaction device (preferably oxygen fuel cell) to generate electrical power; useful for an electronic equipment for operation of electronic equipment by using electrical power generated by the device (claimed).    ADVANTAGE - The reaction device comprises reactor in first container, which is enclosed in second container, with atmospheric pressure in space between containers lower than normal atmospheric pressure; and provides improved reduction of heat dissipation from reaction area to ambient environment, as compared to that achieved in prior art devices, where for reformer as a high temperature area in inner shell of container, inner shell is further housed in outer shell of container, followed by maintaining pressure in spacer layer arranged between inner and outer shells lower than normal atmospheric pressure. Also, by forming metal film low radiation rate layers on inner wall surface and outer wall surface of first container and inner wall surface of the second container, heat transmission from fuel cell is reduced. A mirror-like finishing can also be used instead of metal film low radiation rate layers to reduce the radiation rate. Thus, by high insulating quality due to combination of heat insulating by allowing atmospheric pressure of first and second containers to be lower than normal atmospheric pressure, and heat radiation insulating with the low radiation rate layers; a temperature rise of the fuel cell is accelerated. The fuel cell is heated by thin film heaters/temperature sensors up to 600-800 degrees C which is its operation temperature. Thus, since an operation temperature of solid oxide type fuel cell is as high as 600-800.degree degrees C, carbon monoxide can also be used as a fuel, so that electric power generation efficiency is improved. Further, as the gas injected to a space between reactor and first container, is chosen as gas having smaller thermal conductivity in comparison with air (e.g. carbon dioxide, freon gas, Ar, Kr, Xe and Rn; preferably Xe having small thermal conductivity of 1.9x 10-2 W/Km at 1000 degrees C, which is a quarter in comparison with a thermal conductivity of air at 100 degrees C of 7.6x 10-2 W/Km), the transfer of heat quantity from fuel cell to heat insulating container through gas is prevented. As a result, heat dissipation from reaction area to ambient environment is prevented, and temperature rise in reaction area is accelerated.    DETAILED DESCRIPTION - A reaction device (300) comprises: a reactor (200) to cause a reaction of a reactant; a first container (1) to house reactor; and a second container (2) to house first container, where a gas is injected to a space (13) between reactor and first container and first container is sealed, and an atmospheric pressure in a space (23) between first container and second container is lower than a normal atmospheric pressure. The reactor includes a flow path through which reactant flows, the flow path is communicated with space between reactor and first container, and pressure of gas is adjusted so that a stress which occurs in a wall forming flow path by difference between pressure of reactant and pressure of gas is less than or equal to a fracture stress of wall (preferably the pressure (P) of the gas meets a specified equation as given in the specification). The gas has a smaller thermal conductivity than air. A radiation rate of a part of inner wall surface (14) of first container, a part of outer wall surface (15) of first container, and a part of inner wall surface (16) of second container is lower than a radiation rate of outer wall surface of the second container. The part of inner wall surface of first container, part of outer wall surface of first container, and part of inner wall surface of second container are subjected to mirror-like finishing. The reaction device further comprises a feeding tube through which reactant to be supplied to reactor flows, is connected to the flow path, and is communicated with space between first and second containers. The reactor is a fuel cell that generates electric power by electrochemical reaction of fuel and oxygen. The reaction device further comprises a reformer to produce a reformed gas from raw fuel that is material to produce fuel; and catalyst combustor to perform combustion of an offgas discharged from fuel cell, where reformer and catalyst combustor are placed in space between first and second containers. An INDEPENDENT CLAIM is included for an electronic equipment comprising: the reaction device, in which the reactor is a fuel cell that generates electric power by electrochemical reaction of fuel and oxygen; and an electronic equipment body to operate using electric power generated by fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows a longitudinal sectional view of internal structure of the reaction device.    First container (1)    Second container (2)    Space between reactor and first container (13)    Low radiation rate layer on inner wall surface of first container (14)    Low radiation rate layer on outer wall surface of first container (15)    Low radiation rate layer on inner wall surface of second container (16)    Space between first and second containers (23)    Reactor/fuel cell (200)    Reaction device (300)