In a vehicle, a first gas sensor detects a hydrogen gas concentration of a vehicle interior front zone. Air-conditioning corresponding to an operation of a suction air switching button or the like is performed until the hydrogen gas concentration of the vehicle interior front zone reaches a predetermined second reference concentration, and any one of interior air mode switching control of an interior/exterior air switching mechanism and stop control of a blower is performed regardless of the operation of the suction air switching button or the like when the hydrogen gas concentration reaches the second predetermined reference concentration.