A micropump provided with a cylindrical body (1) containing a measuring chamber (10) defined by a piston (2) and communicating firstly with a tank via an inlet orifice (10a) provided with an inlet valve, and secondly with the outside via an outlet orifice (10b) provided with an outlet valve, the micropump being characterized in that the piston (2) is connected to an external reciprocating actuator, and in that at least one of said valves is constituted by a valve member (3, 6, 7) suitable for being driven in translation by friction contact with said piston (2) successively in one direction and then in the other, and whose stroke inside the chamber (10) is shorter than the stroke of said piston.