NOVELTY - A reactor (1) comprises an external flow pipe (10) having one end joined to a low-temperature reaction unit (6) and having flow pathways including a flow pathway for supplying a first reaction material to a high-temperature reaction unit (4) through the low-temperature reaction unit, and a flow pathway for discharging the product from the high-temperature reaction unit through the low-temperature reaction unit.    USE - Used for forming a liquid fuel, preferably for generating hydrogen to be supplied to a fuel cell, and useful in an electronic device or apparatus e.g. notebook personal computer, personal digital assistant, electronic notebook terminal, digital camera, cellular phone, wrist watch, register, and a projector.    ADVANTAGE - The reactor produces temperature differences between a section causing reaction at a high temperature and a section causing the reaction at a low temperature; prevents an excessive amount of stress from acting on connecting portions between the sections causing the reactions; and reduces heat losses. Since heat transfer can easily be accomplished through the pipe component, efficient heat exchange can be performed.    DETAILED DESCRIPTION - A reactor comprises:    (1) a high-temperature reaction unit, which causes a first reaction of a first reaction material to create a second reaction material and a product;    (2) a low-temperature reaction unit, which causes a second reaction of the second reaction material at a temperature lower than in the high-temperature reaction unit;    (3) a coupling pipe (8), which is interposed between the high-temperature reaction unit and the low-temperature reaction unit, and which transfers the first reaction material and the product created with the first reaction material between the high-temperature reaction unit and the low-temperature reaction unit; and    (4) an external flow pipe having one end joined to the low-temperature reaction unit and having flow pathways including a flow pathway for supplying the first reaction material to the high-temperature reaction unit through the low-temperature reaction unit, and a flow pathway for discharging the product from the high-temperature reaction unit through the low-temperature reaction unit.    An INDEPENDENT CLAIM is included for an electronic apparatus.    DESCRIPTION OF DRAWING(S) - The figure is a perspective view of a microreactor module as viewed from a slant upper side.    Reactor (1)    High-temperature reaction unit (4)    Low-temperature reaction unit (6)    Coupling pipe (8)    External flow pipe (10)