Disclosed is an opening/closing of a mobile terminal, which comprises: a housing having a polygonal section and being non-rotatably inserted into a hinge of a cover constituting the mobile terminal; elastic means inserted into the housing; a rotary cam shaft provided at one end with an insertion shaft which is inserted into the elastic means in a close contacting manner and non-rotatably contained within the housing, and at the other end with opposed cam faces, each of the cam faces being unintermittently constituted of an escarpment a, a top b and an inclination c; a shaft penetrating the rotary cam shaft, the elastic means and the housing in sequence, the shaft being provided at one end with a stepped recess into which a snap ring is fastened to prevent the shaft from being released from the housing.