To provide a cutting tool for facilitating work for cutting a sidewall of a ceiling backing material.

The cutting tool 10 is constituted of a lower operation part 2 and an upper operation part 3 extending in one direction with a shaft part 1 as the base end, and the lower operation part 2 and the upper operation part 3 can relatively rotate with the shaft part 1 as the center. The lower operation part 2 also has a hook-shaped part 4 forming a storage recessed place 4 for storing the sidewall of the ceiling backing material on the shaft part 1 side. Thus, the cutting tool can be used by hooking on the sidewall of the ceiling backing material, and cutting work can be easily performed even in a narrow space above a ceiling board.