To provide a pivoting part structure for an industrial robot, which can effectively prevent crack formation at a crank pin 40.

According to the pivoting part structure, an input gear 48 is spline-connected to the other axial end 40b of the crank pin 40, and an idle gear 54 is rotatably supported not by the other axial end 40b to which the input gear 48 is connected but by one axial end 40a of the crank pin 40. Therefore the crank pin 40 which protrudes from a bearing 41 arranged on one side thereof to support the idle gear 54, need not form a step on the one axial end 40a, the step having been required in order to achieve assembly. As a result, stress concentration at the one axial end 40a caused by bending is prevented.