A fusing unit, and an image forming apparatus including the same, includes: a driving roller; a belt disposed to be driven by the driving roller; a nip plate disposed along a lengthwise direction of the driving roller with the belt being disposed between the driving roller and the nip plate, the nip plate being pressed toward the driving roller to form a fusing nip; a heat radiating body disposed along the lengthwise direction to heat the nip plate by heat conduction; and a heat radiating body pressing member to press the heat radiating body toward the nip plate to prevent the heat radiating body from being spaced from the nip plate due to thermal deformation. The image forming apparatus includes: an image forming unit to form an image on a printing medium with a developer; and the fusing unit.