To execute work safely and easily by integrating a collar into a roll by pressing the side face of the collar to the rolling roll at uniform pressure through each air cylinder.

A jig 20 for fitting a metallic collar ring 50 on the rotary shaft 12 of the rolling roll 10 or pulling it out consists of two metallic rings 22, 22a arranged at a prescribed interval. Metallic bases are provided between the metallic rings 22, 22a at prescribed intervals in the longitudinal direction. Metallic L-shaped flanges 26 are stably held by slightly projecting the upper part corresponding to each metallic base with the metallic ring 22 situated on the side of the metallic collar ring 50. A bolt 32 is screwed into the tapped hole of the metallic L-shaped flange 26 and a lead buffer part 32a is integrally fixed at the tip of the bolt 32. This jig is constituted so that an air cylinder 34 is connected to the rear end of the bolt 32, the bolt 32 is screwed in the tapped hole by driving the air cylinder 34 and the ring is pressed by bringing the lead buffer part 32a into contact with the side face of the metallic collar ring 50.