A coaxial starter including: a motor (25) having a tubular armature shaft (26) to which an armature (23) and a commutator (24) are attached; an output shaft (28) arranged at the front end side of the motor (25) and having one end provided with a pinion (33) disengageably engaged with a ring gear of an engine and the other end inserted into the inside path (26a) of the tubular armature shaft (26) so as to be axially slidable, the output shaft (28) having a large-diameter portion thereof; a driving power transmission device (29) having an overrunning clutch (31) for transmitting rotation force of the armature shaft (26) through the overrunning clutch (31) to the output shaft (28); a bearing (32) provided between a front end surface of the armature shaft (26), perpendicular to the axial direction thereof and the end surface of the large-diameter portion of the output shaft (28); and an electromagnetic switching unit (34) provided on a rear end side of the motor for energizing the motor and for sliding the output shaft (18).
