An image forming apparatus including an image forming device forming a toner image on a recording material, and a fixing device including an endless fixing belt feeding the recording material at a speed of 400 to 1,700 mm/sec while heating to fix the toner image thereon. The fixing belt has a rubber layer located on a substrate and having thickness of 400 μm to 700 μm, and a fluorine-containing resin layer located on the rubber layer and having thickness of 2 μm to 20 μm. The toner includes a release agent including a microcrystalline wax and/or a synthetic ester wax, and a binder resin including a crystalline polyester and an amorphous polyester. The ratio (W/R) of the height (W) of the third falling peak of the crystalline polyester to the height (R) of the maximum rising peak of the amorphous polyester in the FT-IR spectrum of the toner is 0.045 to 0.850.