An apparatus and method for controlling the power supplied to a fixing unit are provided. The apparatus includes a voltage detector detecting a voltage of input power supplied to heat at least one heating lamp, a synch signal generator generating a synch signal in response to the detected voltage, a switching unit switching a supply path of the input power to be applied to the at least one heating lamp, and a controller having table information of temporal duty level values of the input power that is initially supplied, and outputting a control signal for controlling a switching operation of the switching unit using the generated synch signal and the table information, wherein the switching unit performs the switching operation corresponding to the control signal. Accordingly, by sequentially increasing the input power for initial heating of the heating lamps, flickering and harmonic characteristics of a display device can be reduced, and by setting the duty level values to supply the maximum input power within a certain time, an initial heating time of the heating lamps can be minimized.