A fixing device according to the present invention includes a fixing belt (22), a pressuring member (23), a heat source (24), a reflecting member (25) reflecting the radiant heat radiated from the heat source (24) to an inner circumference face of the fixing belt (22), a pressing member (27) pressing the fixing belt (22) to a side of the pressuring member (23) and a supporting member (26) supporting the pressing member (27). The reflecting member (25) is arranged between the heat source (24) and the supporting member (26) and configured to be curved or bent so as to project toward a side of the heat source (24). Straight lines (L) connecting a center (Z) of the heat source (24) with both end parts of the supporting member (26) in a conveying direction of a recording medium pass through the reflecting member (25).