A fixing device includes a fixing roller, a pressure roller, and a regulation member. The fixing roller includes a roller member and a fixing belt. The roller member includes a shaft which extends in one direction and an elastic layer integrally formed on the shaft. Each regulation member has an annular regulation surface which opposes a side edge of the fixing belt, and is configured to regulate movement of the fixing belt in a rotation axis direction. The regulation surface is inclined relative to a line perpendicular to the rotation axis as viewed on a cross-section parallel to the rotation axis. The regulation surface is inclined from the rotation axis side such that the closer the regulation surface is to an outside, in a radial direction, of the fixing roller, the closer the regulation surface is to a center, in a length direction, of the shaft.