To miniaturize a hinge while maintaining friction in rotation.

The hinge mechanism includes at least a rotary shaft having a collar part in an end part, a rotary shaft holding part constituted of "U-shaped" sheet metal of bending at 90° and a circular arc-shaped spring provided with a hole for penetrating the rotary shaft, and the circular arc-shaped spring is sandwiched between the collar part of the rotary shaft and an intermediate plane of a "U shape", and thereby, the center line of a locking part in the longitudinal direction of the circular arc-shaped spring and the center of the hole for penetrating the rotary shaft of the circular arc-shaped spring, are arranged on the center line in the longitudinal direction of the holding part of a biaxial hinge mechanism for forming friction in the rotation, and the locking part of reducing a width more than a hole diameter is directly formed of a circular arc shape of the circular arc-shaped spring.