A resin pipe 30 and a resin member 31 are fixed to a setting portion 5 provided on the front side of a base 6, and a timing pulley 13 which is provided on the back side of the base 6 and to which a light emission unit 3 is attached is rotated. As a result, the light emission unit 3 applies laser light 20 to a junction 32 between the resin pipe 30 and the resin member 31 while revolving around the junction 32. This makes it easy to fuse and join the entire outer circumferential surface of the resin pipe 30 with the entire inner circumferential surface of the resin member 31, which are variously shaped and sized.