Provided are a tripod constant velocity joint, and a method and a device for assembling the joint. The opening of a through-hole formed in an inner member of the tripod constant velocity joint has formed therein a tapered, reduced diameter section having a diameter tapered from the opening toward the inside. A first annular groove is formed in the side wall of a driving power transmission shaft, and a clip serving as an engaging member is engaged with the first annular groove. A second annular groove is formed in the inner wall of the through-hole in the inner member. In inserting the driving power transmission shaft through the through-hole in the inner member, the tapered, reduced diameter section guides the shaft in such a manner that the clip is contracted toward the bottom surface of the first annular groove. The clip expands and contracts due to the elasticity thereof when the positions of the first annular groove and the second annular groove coincide with each other.