The invention provides a fixing device and an image forming apparatus. The fixing device, includes a fixing member; a pressure member; a nip forming member; a reinforcing member; a heating member; and a flange member including a cylinder inserted in an inner circumference at an edge of the fixing member in an axial direction thereof and a flange fixed on a frame of the fixing device, wherein the cylinder of the flange member includes a notch storing the nip forming member at a part on the circumference, has an arc-shaped outer circumferential cross-section at an area corresponding to an area where the fixing member is heated by the heating member, having a predetermined radius equivalent to a radius of the fixing member, and the arc has a center located at an upstream side in a recording medium feeding direction relative to a center line of the nip forming member in the recording medium feeding direction.