To prevent temperature rise of a power source unit when it becomes difficult to cool the power source unit by cooling water, in a structure of normally cooling the power source unit by the cooling water.

The vacuum pump 1 includes a pump unit 2 and the power source unit 3 for driving control of the pump unit, the pump unit and the power source unit being integrated with or adjacent to each other. The vacuum pump 1 also includes a pipe 30 of the cooling water for cooling the pump unit and the power source unit, and a gas introduction section for introducing gas at a pressure higher than the atmospheric pressure within the power source unit. When it becomes difficult to cool the power source unit by the cooling water because supply of the cooling water to the power source unit is cut off or an amount of supply of the cooling water is decreased, gas such as nitrogen gas for pump purging or compressed air for pump utilities is introduced into the power source unit, and a flow of the gas from the inside of the power source unit to the outside thereof is formed, thereby cooling the inside of the power source unit and preventing the temperature rise of the power source unit.

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