There is provided a reciprocating pump in which it is possible to monitor pump volumetric efficiency and a flow rate with ease and accuracy. A reciprocating pump includes a pump chamber； a suction port which enables a liquid to be suctioned into the pump chamber； a discharge port which enable a liquid in the pump chamber to be discharged； a plunger 7 which is capable of reciprocating in the pump chamber by a motor M； check valves are disposed between the pump chamber and a flow route on the suction port side and a flow route on the discharge port side, are openable and closable in response to a change in a liquid pressure in the pump chamber, which is produced due to the reciprocating of the plunger 7 a detection device that is able to detect a period of time during which the check valve is in an opened state or in a closed state in a predetermined cycle； and an arithmetic device that performs an arithmetic operation to obtain pump volumetric efficiency or a flow rate based on a comparison between a period of detection time detected by the detection device and a period of time during which the check valve is in the opened state or in the closed state in the predetermined cycle during normal operation.
