NOVELTY - A fuel cell system comprises fuel cell, modifier (12) which generates reformed gas and has catalyst storage chamber (123) for modification in which catalyst (122) for modification is accommodated, makes fuel and water react on catalyst for modification, and is supplied to fuel cell, combustor (13) which has catalyst storage chamber (133) for combustion in which catalyst (132) for combustion is accommodated and combustion chamber (131) connected to catalyst storage chamber for combustion, and burns off gas from fuel cell on catalyst for combustion, and chemical thermal storage device (14).    USE - A fuel cell system.    ADVANTAGE - The fuel cell system does not have a burner, which is comparatively expensive.    DETAILED DESCRIPTION - A fuel cell system comprises fuel cell, modifier which generates reformed gas and has catalyst storage chamber for modification in which catalyst for modification is accommodated, makes fuel and water react on the catalyst for modification, and is supplied to fuel cell, combustor which has catalyst storage chamber for combustion in which catalyst for combustion is accommodated and combustion chamber connected to catalyst storage chamber for combustion, and burns off gas from fuel cell on the catalyst for combustion, and chemical thermal storage device arranged between combustors so that heat conduction is possible. Chemical thermal storage device has thermal storage agent accommodation space which accommodates chemical thermal storage agent (142) for generating heat by hydration reaction, evaporator which stores temporarily the water supplied to modifier and is arranged between stored water and chemical thermal storage device so that heat conduction is possible, and modified water supply part which can supply modified water (W1) to chemical thermal storage agent of evaporator. Chemical thermal storage device is arranged adjacent to catalyst storage chamber for combustion, modifier is arranged adjacent to combustion chamber, and evaporator, combustion chamber, and chemical thermal storage device are arranged adjacent to catalyst storage chamber for modification.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional diagram of the unit part of the fuel cell system.    Modifier (12)    Combustor (13)    Chemical thermal storage device (14)    Catalyst for modification (122)    Catalyst storage chamber for modification (123)    Combustion chamber (131)    Catalyst for combustion (132)    Catalyst storage chamber for combustion (133)    Chemical thermal storage agent (142)    Modified water (W1)