An engine (1) of a hybrid vehicle that is to be preheated before being started is connected to a heat accumulator (11) that stores a portion of a cooling water that is kept warmed. During cold start of the vehicle, when a temperature of the cooling water in the heat accumulator (11) is equal to or higher than a temperature of the cooling water in the engine (1) by a preset amount, the cooling water kept warmed in the heat accumulator (11) is fed into the engine (1). The motor (4) is driven to operate the vehicle until the engine (1) is sufficiently preheated.