NOVELTY - A reaction apparatus (10A) comprises a reaction apparatus main component (11) which has reaction portion (13,15) where the reaction material is reacted. The container (20) accommodates the reaction apparatus main component and radiation transmission region (23,25) which transmits the radiation from the reaction apparatus main component. The radiation transmission region is provided with a dielectric material layer (23b,25b) which uses at least two materials selected from aluminum fluoride, barium fluoride, calcium fluoride, dysprosium difluoride and gadolinium oxide.    USE - The reaction apparatus is used for electronic device (claimed) and hydrogen fuel cell for motor vehicles and portable apparatus.    ADVANTAGE - The reaction apparatus enables the transmission of radiation of appropriate wavelength region from the main component to exterior of heat insulation container.    DETAILED DESCRIPTION - A reaction apparatus comprises a reaction apparatus main component which has reaction portion where the reaction material is reacted. The container accommodates the reaction apparatus main component and radiation transmission region which transmits the radiation from the reaction apparatus main component. A dielectric material layer is provided in the radiation transmission region. The dielectric material layer uses at least two materials selected from aluminum fluoride, barium fluoride, calcium fluoride, cerium fluoride, cerium oxide, cesium iodide, dysprosium difluoride, gadolinium oxide, lanthanum fluoride, lanthanum oxide, lithium fluoride, diamond-like hard carbon (DLC), magnesium fluoride, lead fluoride, scandium oxide, strontium fluoride, tantalum pentoxide, titania, yttrium fluoride, yttrium oxide, zinc oxide, zinc sulfide, alumina, bismuth oxide, bismuth fluoride, cadmium selenide, cadmium sulfide, cadmium telluride, chromium oxide, gallium arsenide, germanium, hafnium dioxide, magnesium oxide, sodium fluoride, sodium aluminum fluoride (Na3AlF6), sodium aluminum fluoride (Na5Al3F14), niobium pentoxide, neodymium fluoride, neodymium oxide, lead chloride, lead telluride, lead sulfide, antimony trioxide, antimony sulfide, silicon, silicon nitride, silica, tellurium, thallium chloride, ytterbium fluoride, ytterbium oxide, zinc selenide and zirconia. An INDEPENDENT CLAIM is included for electronic device.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of reaction apparatus.    Reaction apparatus (10A)    Reaction apparatus main component (11)    Low-temperature reaction portion (13)    High-temperature reaction portion (15)    Heat insulation container (20)    Radiation transmission region (23,25)    Dielectric multilayer (23b,25b)