To hold the allocation of clearances between the front and the back in the axial direction of a rotor in an appropriate state in a vane compressor by causing a pressure difference between the front and the back in the axial direction of the rotor to balance forces acting on the fronts and the backs of the rotor and a drive shaft formed integrally therewith. In a pair of side blocks (13, 21) which close both ends in the axial direction of a cylinder (12), at least one among an inlet pressure introduction groove which is formed in a surface facing a rotor (3) of one side block (13) and into which a fluid corresponding to inlet pressure is introduced, a groove reduction part (41a) which is formed by reducing, inward in the radial direction of the rotor, part of a portion through which a vane groove becomes openable of an oil introduction groove (41) formed in a surface facing the rotor (3) of the one side block, and a groove enlargement part (42a) which is formed by enlarging, outward in the radial direction of the rotor, part of a portion through which the vane groove becomes openable of an oil introduction groove (42) formed in the other side block is provided.