The invention relates to a medical pump device comprising a rotary valve (13) having preferably only one rectilinear channel (20) which respectively connects the inlet (4) and the outlet (7) of the pump device, or connects the inlet to a pump chamber (15), or said pump chamber to the outlet, upon rotation of the rotary element (19) of the valve. The invention enables a medical pump device to be especially easily produced, said pump device being preferably inserted between an infusion syringe driver or an infusion container and a catheter, and being used to supply small quantities of liquid in an accurately dosed manner.