To provide a boot for a constant speed joint reducing an insertion load in attachment to a counterpart member, and allowing easy determination of whether or not attachment has been accurately carried out.

The boot for a constant speed joint has a small diameter cylinder part held on a shaft, a large diameter cylinder part with a larger diameter than the small diameter cylinder part and coaxially arranged away from the small diameter cylinder part, and a bellows part integrally connecting the small diameter cylinder part and the large diameter cylinder part, and an inner circumferential surface of the large diameter cylinder part is attached so as to press against the counterpart member. A protrusion part protruding to an inner circumference side and engaging with a groove part of the counterpart member is provided on the large diameter cylinder part, and a groove opened to a side face and extending in a circumferential direction is provided on at least one part of the protrusion part.