A fuel cell power plant comprises plural fuel cell stacks (10A 10B) capable of generating power independently, and a warm-up circuit (33) which can independently warm up the fuel cell stacks (10A 10C). A controller (14) estimates a required output power of the power plant within a predetermined time from when the vehicle starts running (S121 S127), and determines the number of fuel cell stacks satisfying the required output power (S106). The controller (14) economizes energy required for warm-up of the fuel cell stacks while providing the required output power by warming up only the determined number of fuel cell stacks before the vehicle starts running.