An image forming apparatus capable of effectively cooling down a recording medium heated by a toner fixing unit includes a cooling mechanism having a duct, a radiating fin, and a heat pipe. The duct includes two air flow structures, each including an air inlet, an air supply path, an air exhaust path, and an air outlet. The radiating fin is arranged between the air supply path and the air exhaust path of each air flow structure. The radiating fin has a plurality of fins each radially extending in parallel to a flow of air in the duct. The heat pipe has one side connected to the radiating fin and another side arranged in a vicinity to an exit of a toner fixing mechanism. The heat pile rotates to draw heat from the heated recording sheet having a fixed toner image.