PURPOSE: To obtain a rotary reciprocating compressor without necessitating the machanism to convert the rotary movement into the reciprocating movement by rotating one columnar member within a cylinder and effecting the reciprocating movement by the sloped surface of the columnar member which rotates the remaining columnar member.

CONSTITUTION: A rotary columnar member 4 within a cylinder 3 provided with a suction opening and a vomitting opening 2 is permitted only to rotate. And, a reciprocating columnar member 5 is permitted only to reciprocate by means of the key or the like provided in the axial direction. As the rotary columnar member 4 rotated, the position of a contact (S) between the rotary columnar member 4 and the reciprocating member 5 moves on the outer peripheral portion of the sloped surface 5 of the reciprocating columnar member 5 towards a point nearest the bottom surface. At the same time, the reciprocating columnar member 5 moves to the rotary member 4 side and thus the space between the columnar members 4, 5 and the inner wall of the cylinder 3 decreases so as to effect the compression function. And, if the rotary columnar member 4 rotaes, the space increases so as to start the suction stroke