Provided is a motorized power steering device which is equipped with a structure wherein it is possible to prevent the occurrence of stick-slip between the outer peripheral surface of a rotation shaft (13) and the inner peripheral surfaces of the inner races (20a, 20b) of anti-friction bearings (19a, 19b). For this purpose, lubricant (24) or an elastic member (25) is interposed between the outer peripheral surface of the rotation shaft (13) and the inner peripheral surface of at least either one of the inner races (20a, 20b). In a case where the lubricant (24) is to be additionally interposed on the rotation shaft (13), the pertinent portion is provided with recessed surfaces which hold the lubricant (24).