A starter with an epicycle reduction gear having a one-way clutch within the casing thereof, which can shut off dust and filthy water, has a simplified structure, has a reduced number of parts and components, has reduced size and weight and has improved durability of the one-way clutch. Such a starter achieves these effects by housing the one-way clutch within the casing of the epicycle reduction gear. The one-way clutch is housed within the casing of the epicycle reduction gear, which includes a plurality of planetary gears. The one-way clutch comprises a small-diameter cylindrical part of the casing, serving as a clutch inner member, a small-diameter cylindrical part of the internal gear, serving as a clutch outer member, fit on the small-diameter cylindrical part of the casing, a clutch roller disposed between the small-diameter cylindrical part of the casing and the small-diameter cylindrical part of internal gear, and a spring. The internal gear includes a large-diameter cylindrical part with an annular face. The one-way clutch is formed so as to have a smaller diameter than the outside diameter of the large-diameter cylindrical part of the internal gear.