PURPOSE: To offer a pumping device with simplified construction and low cost by giving the suction and exhaust ports of a cylinder a packing effect and by making the valve element, which has both functions of suction and exhaust valves in a single construction, from a sheet of elastic substance.

CONSTITUTION: In the head 11 of a cylinder 9 is furnished with a suction 11a and exhaust 11b ports which correspond to the suction 9a and exhaust 9b ports of the cylinder 9, respectively. The valve element 12 is made from a thin sheet of elastic substance and furnished with a suction 12a and exhaust 12b valves formed by notches in the position corresponding to the suction 9a and exhaust 9b ports of the cylinder 9. Because the valve element 12 consists of a thin elastic sheet, the suction 12a and exhaust 12b valves function not only with opening/ closing effect but also packing effect to seal the cylinder 9 and head 11 air- or liquid-tightly.