To provide a reciprocation pump including a single reciprocation head, capable of suppressing pulsation while achieving reductions in size and cost.

In a diaphragm pump 100, a gas is discharged from a pump chamber 1 and a counter chamber 2 to an exhaust pipe 22 when a phase is 0° and 180°. In this manner, the gas is discharged twice during one reciprocation of a diaphragm 5, allowing the pump 100 to obtain an effect similar to that of a pump including two reciprocating heads to suppress pulsation. Accordingly, even the diaphragm pump 100 including only the single diaphragm 5a eliminates the need for a buffer tank, a regulator and the like, allowing the pulsation to be suppressed while achieving reductions in size and cost.