An O-ring has a shape including a first portion that is arranged side by side with a suction port in an axial direction, a second portion that is arranged side by side with a suction port, and a third portion that connects these portions. The first portion and the second portion are arranged to be displaced from each other in the axial direction. The third portion is arranged to extend in a direction different from a circumferential direction between the suction port and the suction port when a pump body is viewed in a radial direction. Thus, the suction ports can be located closer to each other in the axial direction. Therefore, the axial direction length of the pump body can be reduced, and size reduction of a rotary pump device can be achieved.