To vertically move a screen display of a liquid crystal monitor for a personal computer and the like while maintaining the inclination thereof nearly constant.

The supporting arm mechanism is equipped with an upper rotational moving member which pivotally attaches a mounting plate of the screen display and is vertically revolvable, a lower rotational moving member which forms a cam surface in an upper part and is horizontally revolvable, a tiltable arm body which is pivotally attached to the upper rotational moving member and the lower rotational moving member, respectively, and an advanceable and retreatable link bar which is associated with a mounting plate through the upper rotational moving member. When the arm body is tilted downward or upward, a pin fastened to the link bar slides along the cam surface of the lower rotational moving member and the mounting plate of the screen display is maintained in a constant inclination angle by the advance and retreat of the link bar.