Inner surfaces of two guard plates (11a) forming a piping guard (11) abut against end surfaces of nut bodies (13) fixed to opposite left and right side surfaces of an arm (8), and bolt through holes (11c) made in the guard plates (11a) are opposed to attachment positions of the nut bodies (13) corresponding thereto, respectively. Then, front end portions of the bolts (12) penetrating the bolt through holes (11c) are screwed into the nut bodies (13). Thus, the piping guard (11) is attached to the arm (8). Stoppers (14) are attached to places of the inner surfaces of the guard plates (11a) to abut against a front end portion of the arm (8) or against the nut bodies (13), to thereby prevent a shearing force from acting on the bolts (12). Thus, it is possible to provide an attachment structure of a piping guard in which the piping guard can be attached to an arm stably without any shearing force acting on bolts attaching the piping guard to the arm.