Provided is a seat belt retractor capable of having its assembly readily performed to increase assembly efficiency, simplifying shapes of components to readily manufacture the retractor and reduce manufacturing cost, and preventing a webbing from being hooked when the webbing is rewound. The seat belt retractor includes a housing constituting a main body of the seat belt retractor, a guide drum rotatably installed in the housing, a connector inserted into one side of the guide drum, a base member surrounding the connector, a gear member inserted into the base member, a cylinder for operating the gear member, a torsion bar inserted into the guide drum, a locking member fixedly inserted between the torsion bar and the guide drum, a locking clutch installed at one surface of the locking member, a mechanism cover installed at one surface of the locking clutch, and a friction spring installed in the mechanism cover to stop operation of a lock arm fixed to the locking clutch.Therefore, an operator can assemble the base member and the gear member while viewing them. In addition, the clutch rollers rotate while moving outwardly along the slant surfaces of the slant gear to rotate the connector and rewind the webbing. Thus, shock applied to a passenger is lessened.