An image forming apparatus comprising: a toner; an image forming device (60, 8, 10, 5, 61) to form an image of a toner on a recording material; and a fixing device including an endless fixing belt to feed the recording material bearing the toner image thereon at a speed of from 400 to 1,700 mm/sec while heating the recording material to fix the toner image on the recording material, wherein the fixing belt has at least a substrate, a rubber layer located on the substrate and having a thickness of from 400μm to 700um, and a fluorine-containing resin layer located on the rubber layer and having a thickness of from 2μm to 20μm, wherein the toner includes: toner particles including: a release agent including at least one of a microcrystalline wax and a synthetic ester wax; and a binder resin including a crystalline polyester resin and an amorphous polyester resin, and wherein the toner satisfies the following relation: 0.045 ≤ W / R ≤ 0.850, wherein W represents a height of a third falling peak specific to the crystalline polyester resin in a Fourier transform infrared spectroscopy (FT-IR) spectrum obtained by subjecting the toner to FT-IR using a KBr pellet method, and R represents a height of a maximum rising peak specific to the amorphous polyester resin in the FT-IR spectrum, wherein the third falling peak is present between a first falling peak having a minimum absorbance and a second falling peak having the second lowest absorbance, wherein the height W of the third falling peak is defined as the height from a base line obtained by connecting the first falling peak and the second falling peak and wherein the height R of the maximum rising peak specific to the amorphous polyester resin is defined as the height from a base line obtained by connecting the first falling peak and the second falling peak. a toner; an image forming device (60, 8, 10, 5, 61) to form an image of a toner on a recording material; and a fixing device including an endless fixing belt to feed the recording material bearing the toner image thereon at a speed of from 400 to 1,700 mm/sec while heating the recording material to fix the toner image on the recording material, wherein the fixing belt has at least a substrate, a rubber layer located on the substrate and having a thickness of from 400μm to 700um, and a fluorine-containing resin layer located on the rubber layer and having a thickness of from 2μm to 20μm, wherein the toner includes: toner particles including: a release agent including at least one of a microcrystalline wax and a synthetic ester wax; and a binder resin including a crystalline polyester resin and an amorphous polyester resin, and wherein the toner satisfies the following relation: 0.045 ≤ W / R ≤ 0.850, toner particles including: a release agent including at least one of a microcrystalline wax and a synthetic ester wax; and a binder resin including a crystalline polyester resin and an amorphous polyester resin, and a release agent including at least one of a microcrystalline wax and a synthetic ester wax; and a binder resin including a crystalline polyester resin and an amorphous polyester resin, and wherein the toner satisfies the following relation: 0.045 ≤ W / R ≤ 0.850, wherein W represents a height of a third falling peak specific to the crystalline polyester resin in a Fourier transform infrared spectroscopy (FT-IR) spectrum obtained by subjecting the toner to FT-IR using a KBr pellet method, and R represents a height of a maximum rising peak specific to the amorphous polyester resin in the FT-IR spectrum, wherein the third falling peak is present between a first falling peak having a minimum absorbance and a second falling peak having the second lowest absorbance, wherein the height W of the third falling peak is defined as the height from a base line obtained by connecting the first falling peak and the second falling peak and wherein the height R of the maximum rising peak specific to the amorphous polyester resin is defined as the height from a base line obtained by connecting the first falling peak and the second falling peak.