Image forming apparatus and fixing unit control method thereof

An image forming apparatus and a fixing unit control method thereof are provided to control the power supplied to a fixing unit at an initial stage at which the temperature control of the fixing unit is impossible. A fixing unit(120) fixes an image transcribed at a recording medium, and a power supplier(130) supplies power to the fixing unit. A switching unit(140) switches the power supplied to the fixing unit, and a controller(150) controls the switching unit lest power should be supplied to the fixing unit at least one section while performing an initial operation of an image forming apparatus. The controller includes a zero-cross detection circuit which detects a zero-cross spot of the power supplied from the power supplier.