A hinge mechanism 1 includes a rotation shaft 3 connected to a monitor and serving as rotating central axis X; a base 2 pivotally supporting the shaft 3 rotatably, and having click recesses 2b1, 2b2 and a housing position determining recess 2c on a circumference centering the axis X; a plate 5 attached at the end of the shaft 3; and a leaf spring 4 located between the base 2 and plate 5, fit-in by the rotation shaft 3, and having a click projection 4b that fits in the click recesses 2b1, 2b2 and recess 2c to hold the monitor in a predetermined rotation angle position. A sliding friction projection 4c sliding with pressed into contact with the base 2 is formed on the side opposite from the click projection 4b across the axis X, while a cutaway 2e entered by the projection 4c is formed in the base 2.