There is provided a hinge module for mechanically connecting a main body to a folder in a portable radio terminal. In the hinge module, a hinge shaft has an angled portion on one end and a shaft on the other end thereof, for rotating with the folder. A hinge cam is disposed to face the hinge shaft and has a pair of angled portions on the surface facing the hinge shaft, a valley portion between the angled portions, a fixing post along a rotating axis, and a guide protrusion for facilitating sliding of the hinge cam with respect to the hinge shaft while restricting rotational movement of the hinge cam. Each angled portion has a gentle slope and a steep slope that are asymmetrical sidewise. A hinge spring is disposed along the rotating axis and has one end connected to the fixing protrusion of the hinge cam, for providing restoring force to the hinge cam.