To protect a claw piece for preventing fall-off of a modular plug, to improve an insertion/pull-out property, to prevent the coming-off, when connecting, of the modular plug to the protection tool of the modular plug, and to eliminate the contact between adjacent insertion holes of a communication device and a network device.

On the protection tool for a modular plug with cable (10), a front wall of a flat cylindrical body 7 having an insertion port (1) through which the flat cable is inserted is made curved in upper and lower directions and made thick; a curved eaves (3) extending frontward is arranged at a front upper part; two cable insertion guides (4, 5) formed in extension into a tongue-piece shape, having a length almost the same with each other, are arranged at an upper side and lower side of the insertion port (1) located at the front end (8) of the cylindrical body 7; and a square window (6) is formed on the lower side cable insertion guide (5).