PURPOSE: To dispense with drilling of pressure adjusting passages by constituting a pair of pressure adjusting passages communicating the same side parts of respective pump chambers to each other, out of annular grooves formed on the opposed faces between a cam ring and respective side plates, and connecting grooves to connect the annular grooves to the same side parts of the respective pump chambers.

CONSTITUTION: In a vane pump 30 for transmitting torque between an input member 10 and an output member 20, a rotor 32 is relatively rotatably received inside a cam ring 31, a pair of side plates 33, 34 are arranged on both sides of them, and hence a pump chamber CH is defined. For communicating the same side parts of respective pump chambers CH divided by means of a wane to each other, a pair of pressure adjusting passages R1, R2 are formed. In this case, the respective pressure adjusting passages R1, R2 are respectively constituted of respective annular grooves R11, R21 and respective connecting grooves R12, R22 connecting them to the corresponding same side parts of the respective pump chambers CH.