To provide a dust boot to eliminate the need of assembling of a washer for water-proofing to a guide pin, reduce a fastening force during assembly of a seal part on the pin side to a guide pin, and reduce an expansion ratio during assembly of the seal part on the pin side.

In a dust boot 20 for a disc brake to protect a pin slide part consisting of a moving caliper, a guide pin 12 arranged between support bodies, and a guide hole, a cylindrical seal part 21 on the pin side is assembled in an adhesion state to the bottom of an circular groove 12a, formed in the outer periphery of a guide pin 12, through a cylindrical inner periphery seal surface 21a. A taper in a shape that the outer end face side has diameter D2 smaller than the outside diameter D1 of the guide pin 12 and the vertical bisector L of a bus S crosses the inner periphery seal surface 21a at right angles is formed at the outer periphery of the external end part of the seal part 21 on the pin side.