To provide a universal joint and its assembling method capable of firmly fitting and installing a cover member to a shaft part of a joint cross member, and capable of using the cover member large in a dimension in the axial direction without becoming a hindrance to assembling of the universal joint.

This cover member 16 of the universal joint 10 includes a core material 42 having a cylindrical fitting part 44 suitable for an outer peripheral surface of a shaft part 13, and an elastic member 43 having lip parts 53 and 54 brought into pressure contact with an outer peripheral surface 18a of a bearing cup 18 and fixed to the core material 42. The outer peripheral surface of the shaft part 13 is formed with a fitting object surface 27 fitted with the fitting part 44, and a regulating projection part 28 for regulating the movement to the chip side in the axial direction of the fitting part 44 by projecting outward in the radial direction on the tip side in the axial direction of this fitting object surface 27. The fitting part 44 is elastically deformably formed in the diametrically expanding direction so as to be fittable to the fitting object surface 27 by getting over the regulating projection part 28 from the tip side of the shaft part 13.