A swaging tool for fastening a pair of plate members sewages a collar fitted to a pintail side of a fastening pin, where a pinhead of the fastening pin is positioned on one of the plate members and the pintail of the fastening pin is positioned on the other plate member, to the fastening pin with the collar being in contact with the other plate member and to apply a tensile load to the pintail to break off and remove the pintail. The swaging tool includes a holding member that holds the pintail of the fastening pin, a swaging member having a swaging die that comes into contact with and sewages the collar, and a stroke mechanism configured to expand and contract a space between the swaging member and the holding member. The stroke mechanism includes a rotatable rotary member that converts a rotation of the rotary member to the expansion and contraction of the space between the holding member and the swaging member and restricts a rotation of the swaging member and a rotation of the holding member.