An image forming apparatus includes a fixing unit including a fixing belt having a surface to which a lubricant is applied, a heater contacting the surface and including heating elements arranged along a width direction of the belt and including first end second end heating elements and a central heating element, and a pressing roller capable of pressing and rotating the belt, a power supply configured to supply power to the heating elements, and a controller configured to determine a first amount of power to be supplied to the central heating element and a second amount of power to be supplied to each end heating element such that the first amount is greater than the second amount, and control the power supply to supply the first and second amounts to the central heating element and each end heating element before controlling the pressing roller to rotate.