A fixing unit fixes the toner image on a sheet by causing the sheet carrying a toner image to pass through a nip portion formed by bringing a rotary fixing member and a rotary pressing member into pressure contact with each other. The image forming apparatus includes an image forming apparatus main body having a fixing unit accommodating portion for accommodating the fixing unit in an insertable and removable manner, and a heating unit provided in the image forming apparatus main body and heating a rotary fixing member of the fixing unit mounted on the fixing unit accommodating portion from outside in a radial direction. The direction in which the fixing unit is inserted into and removed from the fixing unit accommodating portion coincides with the axial direction of the rotary pressing member.