A boot for a universal shaft coupling, by which an improvement of an assembling workability can be expected, and an improvement of a sealing performance can be expected. The boot for the universal shaft coupling is formed by a rubber elastic body, and separated portions (22) are formed linearly along a generatrix. A fastener pair (26) is arranged in both sides of the separated portions (22) so as to form a seal portion. The fastener pair (26) is constituted by an occluding portion (32) formed in one end edge of the separated portion (22) and provided with a bulge locking portion (32a) in a leading end, and an occluded portion (34) formed in another end edge of the separated portion (22) and provided with an occluding groove (33) occluding with the bulge locking portion (32a). A guide fin (36) is provided in an inner side of the occluding groove (33) on a separated portion end surface (22b) in a side forming the occluded portion of the separated portion (22), in a side of a crest portion (28) of a bellows portion (24). The guide fin (36) is provided a guide surface (40) at a position partly overlapping the occluding portion (32) at a time of facing to the occluding portion (32).