A metering pump for feeding out viscous materials, which pump comprises a housing having an inlet connectable to a viscous material source, an outlet; and a valve body of cylindrical basic shape, which is rotatable into at least two positions by means of a drive unit including a first position allowing a flow of the material from the inlet to the housing and a second position allowing a flow of the material from the housing to the outlet. The pump also comprises a cylinder device connected to the housing, having a controllable piston intended to achieve the flow of material, and at least one device for cleaning the metering pump. The cleaning device comprises at least one nozzle for cleaning agent, disposed in a valve-body-facing part of the piston. Also, a method for cleaning such a metering pump.