It is an object of the invention to, even in the case where liquid containing a sedimenting material such as slurry is used, prevent sedimenting and aggregation from occurring in a pump. As means for attaining the object, a bellows 7 that is extendingly and contractingly deformable in the axial direction is placed in a pump body 1 with setting the axis B of the bellows vertical so as to be driven to perform extending and contracting deformation, and form a liquid chamber 9 inside the bellows 7. A suction port 18 and a discharge port 19 are formed in an inner bottom face 4a of the pump body 1 facing the liquid chamber 9. Liquid is sucked from the suction port 18 into the liquid chamber 9 by extension of the bellows 7, and the liquid in the liquid chamber 9 is discharged from the discharge port 19 by contraction of the bellows 7. The inner bottom face 4a is formed into a conical shape in which the face is downward inclined as moving toward the discharge port 19. Therefore, also liquid containing a sedimenting material such as slurry can be always smoothly discharged toward the discharge port 19 along the downward inclined face of the inner bottom face 4a without collecting on the inner bottom face 4a of the liquid chamber.