A hinge apparatus includes an upper body, a lower body, a shaft whose lower end portion is rotatably installed in the lower body, a piston whose outer circumference is slidably installed along the inner surface of the lower body, a rotational/linear motion converter which converts a rotational motion of the shaft into an axial linear motion of the piston, a damping unit provides a damping function selectively where the piston ascends according to return of the door, a torsion spring rotates the shaft in the door closing direction, and a clutch unit for stopping the elastic force due to reverse twisting of the spring or for restoring the elastic force of the spring.