To provide a reciprocating compressor capable of stably driving even when an electric motor with small inertia is used.

A motor drive control device 22 is connected to the electric motor 3 driving a compression part 4. A control part 30 of the motor driving device 22 controls motor power Pm supplied to the electric motor 3 based on a rotational position θ by a rotation sensor 20. The control part 30 calculates the maximum load PM of the compression part 4 by using a pressure detection value P of a tank 18 when the load of the compression part 4 is large, and supplies the electric motor 3 with the motor power Pm increased more than power source power P0 to overcome the maximum load PM. Also, the control part 30 supplies suction stroke power P2 reduced less than the power source power P0 when the load of the compression part 4 is small.