To provide a pump to satisfy a highly hygienic demand for a long period of time.

A pump 20 has a rotor 80 in a pump passage 25, the rotor 80 has a pump element 90 furnished with a waveform boundary surface extending in the radial direction, the boundary surface moves by closely fitting itself in a cylindrical force feeding region 27, the highest point moves along an end surface of the pump passage by making contact with the end surface 35 of the pump passage, and a seal slider 31 free to shift in parallel against an axis of rotation 76 is provided. Consequently, the seal slider seals the pump passage 25 between an inlet and an outlet, consequently, the rotor 80 follows waveform motion of the boundary surface 96 of the pump element at the time of rotation, a sealing means to seal a pump chamber passing a medium against a casing is provided, the rotor 80 is connected to a driving shaft 180 free to dissociate while forming a connected boundary surface, and the connected boundary surface is arranged on the side of a drive device and on the opposite side of the sealing means.