Water pump

A water pump comprising:

• a rotary member that rotates by drive force from a power source;
• a pump shaft that rotates around an axis line by drive force of the rotary member;
• an impeller provided on one end of the pump shaft;
• an electromagnetic clutch that has a hub member provided on the other end of the pump shaft to rotate integrally with the pump shaft and switches between a transmission state where the rotary member and the hub member are made to frictionally engage to transmit drive force of the rotary member to the pump shaft and a cutoff state where frictional engagement of the rotary member and the hub member is released to cut off transmission of drive force from the rotary member to the pump shaft;
• and
• a flange member provided on the hub member to rotate integrally with the pump shaft, wherein
• the rotary member has a first magnet retention portion retaining a first permanent magnet,
• the flange member has a second magnet retention portion retaining a second permanent magnet, and
• the water pump is configured such that when in the cutoff state, by magnetic attractive force between the first permanent magnet and the second permanent magnet, the flange member is rotated together with the rotation of the rotary member.