Desired is a function of tilting up a steering wheel to allow a driver to get on or off easily. An object of the invention is to strengthen the coupling between a steering wheel and a steering boss and reduce the degree of backlash by using a ball and a ball receiving dent to couple the steering wheel to the steering boss and increasing the pressure applied to the ball, and to provide smooth coupling between the steering wheel and the steering boss by holding the ball from inside as a coupling member tending to protrude from a tapered hole and smoothly guiding the ball into a recess for coupling.