POSITIVE-DISPLACEMENT MACHINE

There is provided a displacement machine comprising a cylindrical guide member; a reciprocating member provided with a piston portion configured to have a reciprocating motion and a swinging motion in the cylindrical guide member; a pair of first arm portions mounted to the reciprocating member; a pair of shaft members arranged to be symmetric with respect to a center axis of the cylindrical guide member; and a pair of second arm portions provided to respectively support the pair of first arm portions at positions displaced from rotation axes of the pair of shaft members. The pair of first arm portions and the piston portion are mounted such that an angle between a center axis of the pair of first arm portions and a center axis of the piston portion is displaceable by a predetermined small angle from 90 degrees and that the pair of first arm portions are movable in parallel by a predetermined small distance in a direction perpendicular to the center axis of the piston portion.