A variable displacement pump comprising an outer housing (10, 30), a drive space (12) being formed in the interior thereof. A swash plate (35) is positioned in the drive space (12) and mounted in such a way as to allow rocking centered on brackets (34), and adjustment of the angle of inclination of an inclined surface (36). A cylinder block (50) is mounted in the drive space (12) and rotates under the action of a drive shaft (90), multiple cylinder holes (55) being formed in the interior of the block and extending in a direction parallel to the drive shaft (90). A piston assembly (70), at least a portion whereof is inserted into the cylinder holes (55) of the cylinder block (50), moves rectilinearly therein while rotating along with the cylinder block (50). A retainer plate (80), being connected to the piston assembly (70) and holding same close to the inclined surface (36) of the swash plate (35), rotates along with the piston assembly (70). An incline adjustment part (100) passes through the outer housing (10, 30) and is extendable and retractable within the drive space (12), and one side thereof, when inserted into the interior of the drive space (12), is used to push the bottom surface of the swash plate (35) and thereby adjust the angle of inclination of same.