Abstract: An opening/closing apparatus of a damper for adjusting a blowing amount of air out of an air diffuser comprises a case mounted at the center of the diffuser in a predetermined size and shape and having an indicating scale portion to be properly positioned at the front surface thereof; a rotating shaft passed through the center portion of the case and extended in a predetermined length out of the case; a rotating manipulation portion including a knob integrally fixed to one end of the rotating shaft; and an indicating operation portion cooperated with the rotating manipulation portion to enable an indicator to direct the indicating scale, thereby confirming the exact opening or closing degree of the damper.