PURPOSE: To provide an inexpensive and favorable retracter for a seat belt capable of smoothly rotating a wind-up shaft by way of absorbing a clearance in the shaft direction of the wind-up shaft of the retracter.

CONSTITUTION: An emergency lock mechanism is covered by a sensor cover 24 arranged on the outside of a base side plate 1b. A tapping screw 20 is spirally attached on an end part of a wind-up shaft 4 around which a webbing 40 is wound, and a projection part 34 projected toward the inside of a retracter so as to make contact with the head part of the tapping screw 20 after installation and an elastically deformable thin part 35 formed on the circumference of the projection part 34 so that the projection part 34 can energize the wind-up shaft 4 elastically in the shaft direction are provided on a bottom wall part 24a of the sensor cover 24 facing against the tapping screw 20.