A starter with a planetary reduction gear mechanism, in which an output shaft (220) has its one end protruded from a bearing (440) of a housing (400) and is arranged at its protrusion with an output shaft retaining member (including a retaining member (10) and a washer (20)) having an external diameter larger than the internal diameter of the bearing (440) of the housing (400). The output shaft (220) is regulated in its axially backward movement not by a radially spaced rear end face of a center bracket (360) and a motor partition (800) but by the output shaft retaining member and the housing (400) so that the axially backward movement of the output shaft (220) can be reliably regulated.
