In a cooling system of liquid type, dissolving a problem upon starting when applying a centrifugal pump therein, and being freely applicable into various kinds of electronic apparatuses, easily, for cooling a CPU in need of cooling thereof, which is mounted within a housing 100, the system comprises: a cooling jacket 50, a radiator 60 and a circulation pump, wherein the circulation pump is built up with a centrifugal pump, in which a rotor 730 having a plural number of blades formed in a centrifugal manner, a pump chamber 741 receiving the rotor in an inside thereof, and a field coil 712 of an electric motor for driving the rotor rotationally are formed into one body, and the pump chamber is disposed to located below the electric motor, thereby achieving the structure so that a liquid coolant fills up the pump chamber when stopping, in spite of the disposition of the circulation pump, thereby dissolving the problem of idling when starting.