A starter includes a drive shaft having an outer periphery formed with shaft splines through which a drive power is transmitted from a starter motor, an overrunning clutch, having an inner periphery formed with barrel splines engageable with the shaft splines, which is axially moveable with respect to the drive shaft and plays a role as one-way clutch, and a pinion gear integrally disposed on the overrunning clutch to be movable into or out of meshing engagement with a ring gear of an internal combustion engine. A radial clearance between a tooth top of each shaft spline and a tooth bottom of each barrel spline is set to be less than a backlash between each shaft spline and each barrel spline.