In an oil passage structure for a power transmission device including a case provided to accommodate a power transmission device, a baffle plate attached to an inner wall of the case, and an oil pump, the oil passage structure includes a supply oil passage through which oil is pumped from the oil pump to an oil supply destination via the baffle plate. The baffle plate has a structure in which two members of a plate body and a plate-shaped auxiliary member are superposed and integrated with each other. The baffle plate is provided with a plate oil passage that constitutes a portion of the supply oil passage and passes through the inside of the baffle plate. The plate oil passage is formed by a recess provided in at least one of a surface of the plate body and a surface of the auxiliary member which face to each other such that the auxiliary member is interposed on the plate body.