A device for automatically adjusting an angle of a monitor on a vehicle seat back includes: a fixation bracket on a front seat back upper-frame; a first rotation bracket on an upper portion of the fixation bracket; a second rotation bracket on a lower portion of the fixation bracket; a monitor on a front surface of the first rotation bracket; a motor on a bottom surface of the second rotation bracket; an angle adjustment bar integrally combined with a rear surface of the first rotation bracket; a lead screw, whose lower portion is connected to an output shaft of the motor, and whose upper portion passes through the second rotation bracket; and an ascending and descending member having a threaded hole such that the ascending and descending member fastened to the lead screw while being fastened to an end portion of the angle adjustment bar.