To provide a protection tool for connection optical member which is superior in moldability and assemblability and consists of a pair of semicylindrical bodies having a firm junction surface.

A pair of semicylindrical bodies 2 and 3 are provided with groove parts 2A, 2B, and 3A, 3B facing each other along outer peripheral surfaces orthogonal to their axial directions, and this pair of semicylindrical bodies 2 and 3 are made abut into a cylindrical body 4, and slit rings 5 and 6 are fitted to circular groove parts A and B formed on the cylindrical body 4, thus constituting a protection tool 1.