A solid oxide fuel cell system includes: a fuel cell unit including a solid oxide fuel cell and a mixer, the solid oxide fuel cell including an anode gas passage and a cathode gas passage, the mixer mixing an anode off gas discharged from the anode gas passage and a cathode off gas discharged from the cathode gas passage; a power-generating raw material supply device operative to supply a power-generating raw material to the fuel cell unit; a combustible gas passage, which extends from the power-generating raw material supply device to a downstream end of the anode gas passage; an oxidizing gas supply device operative to supply an oxidizing gas to the cathode gas passage; and a controller operative to, after electric power generation by the fuel cell unit is stopped, control the power-generating raw material supply device to supply the power-generating raw material in a volume more than or equal to a volume of the combustible gas passage to the combustible gas passage, and concurrently control the oxidizing gas supply device to supply the oxidizing gas to the cathode gas passage.