To provide a urethane coupling, filling a space between a pair of circular hubs while removing bubbles in liquid urethane.

The paired circular hubs 2, 3 having two or more projections 6, 7 at the end face and center holes 4, 5 are positioned so that the projections 6, 7 engage with each other at a space between them. The liquid urethane is caused to flow into the space by centrifugal force, and urethane elastomer formed by reacting and hardening the liquid urethane while the centrifugal force is kept is interposed in the space, the end faces of the paired circular hubs 2, 3 are joined to each other through the urethane elastomer 8.