PURPOSE: To provide a new inovated elastic ring fitting machine, with which an elastic ring can automatically be fitted in a groove provided at the periphery of a pipe.

CONSTITUTION: A ring fitting machine concerned is furnished with an elastic ring enlarging/contracting device 10, in which a plurality of slide pawls 11 are installed concentrically so as to be capable of holding an elastic ring 2 and are arranged as enlarging and contracting in the circumferential direction, and a pushout device 30, in which a pushout member 33 enlarging and contracting in a single piece with the slide pawls 11 and having a ring receptacle 37 is provided with possibility of advancing and retreating in the direction fore and aft. When enlarged, the slide pawls 11 holds the elastic ring 2 in such a condition as enlarged wider than the dia. of a pipe in cooperation with the receptacle 37 of the pushout member 33. When advanced, the pushout member 37 sets off the ring 2 from the slide pawls 11 for partial contraction, and thereby the contracted part is fitted in a groove formed in the pipe.