Abstract: Disclosed is a controller mounted on a hybrid vehicle. The hybrid vehicle has a plurality of heat generating components such as an engine, and a plurality of cooling conduits through which a fluid flows for cooling said plurality of components. A controller decides whether or not the engine is in a warmed-up condition and the components whose rejected heat is utilized are in a warmed-up condition. The components whose rejected heat is utilized comprise at least one of a plurality of components mounted on the hybrid vehicle except the engine. The controller serves to form flow passages between the cooling conduit associated with the engine and the cooling conduit associated with the components whose rejected heat is utilized in the case where it is considered that the engine is not in a warmed-up condition, but the components whose rejected heat is utilized are in a warmed-up conditions.