To provide a variable displacement pump capable of reducing both of driving horsepower and slide loss horsepower of the variable displacement pump by a simple structure.

A main pump 11 rotates and drives a main pump rotor 22 to suck working fluid through a main pump inlet port 23 and discharge it through a first main pump discharge port 24 and a second main pump discharge port 25, respectively. A subpump 12 rotates and drives a subpump rotor 42 by the working fluid supplied into a driving force generation port 43 to suck it through a subpump inlet port 44 and discharge the sucked working fluid together with the working fluid supplied into the driving force generation port 43 through a subpump discharge port 45. A selector valve 31 switches the second main pump discharge port 25 and an internal combustion engine or the driving force generation port 43 selectively and communicates them.