To provide a fixed constant velocity universal joint which can be reduced in weight and compactified, and a boot which can be used for such a fixed constant velocity universal joint and can be compactified.

An outside joint member 2 has a mouth 22 in which an internal component S constituted of at least an inside joint member 1, a ball 3 and a gage 4 is accommodated. The axial length of the mouth 22 is made to be a corresponding short length within at least an operation angle of a high use-frequency range of a practical use zone. By this arrangement, while the operation angle of the constant velocity universal joint is 0°, an end at the joint-opening side of the gage 4 is made to protrude outward rather than an opening of the outside joint member 2. The number of mountains 20 and valleys 19 of a bellows 14 is two, respectively. Within at least the operation angle of the high use-frequency range of the practical use zone, a boot shape and a boot film length are set so that the internal component S does not contact with the internal face of the bellows.