is such that rollers 20 are pressed against a tube 21 as they move thereby compressing the tube 21 so that the liquid in the tube is transferred forward in successive order the number of rollers can be suitably determined according to the required rate of liquid transfer for the purpose of blood pumping for example a 2 roller type roller is normally used the liquid transfer pipe 11 may be a stainless steel pipe or a resin tube or a flexible plastic tube a flexible pvc tube is usually employed for transfer of blood or the like where such flexible tube is used the pressure applied to the interior of the tube while the tube is shut off by the valve can be absorbed through inflation of the tube where a rigid tube e g a stainless steel tube is used however a prolonged shut off period may result in pump break down because the tube has no means to absorb the pressure therefore in the case of a rigid tube being used it is desirable that a chamber 13 for pressure absorption be provided in the line the membrane module 30 incorporates membranes of hollow fiber shape or cylindrical shape or flat plate shape as is known such membrane may be of ethylenevinyl alcohol copolymer cellulose derivative such as cellulose acetate or the like polyolefin polyacrylonitrile polyamide.