In the expander (50) in a drum brake, when the brake is activated, the sleeve (56) is extended in the lateral directions in the drawing by the wedge (52) inserted within the housing (51), and the shoe engaged with the clip (58) is swung to press the lining (23) against the drum, and friction braking is performed. When the lining (23) wears away and the amount of movement of the sleeve (56) increases, the sleeve (56) is rotated by reciprocal action with a drive ring (62) that is engaged with the periphery of the sleeve and, thereby, the pressing screw (57) screwed thereon comes out by the amount of the increase of movement (the amount of wear on the lining). A flat surface (56c) is formed on the periphery of the sleeve and the detecting head (80) of the displacement detection apparatus detects the rotation of the sleeve (56).