To solve a problem that in a gear pump, an engagement portion of a gear produces a confining zone in which operation fluid is confined, and sudden pressure fluctuation in the confining zone causes vibration and noise.

The confining zone 24 is produced between an engaging points A and B of a driving gear 7 and a following gear 8. A side plate is provided with a recessed portion 18 on a side surface of the gear. An elastic material such as synthetic rubber 19 is received in the recessed portion 18. The recessed portion 18 faces the confining zone 24, and is disposed between clearance grooves 20, 21 while evading a line of action K of engagement of the gears 7, 8. Pressure fluctuation in the confining zone 24 is attenuated by expanding and contracting the elastic material 19, thereby preventing generation of vibration and noise.