An induction heating type fixing apparatus comprises a fixing sleeve formed of a flexible thin electrically conductive magnetic material, a coil for producing an induced eddy current in the fixing sleeve to generate heat therein, a holder adapted to retain the coil and disposed stationarily in the fixing sleeve, and a pressing roller pressed against the holder through the fixing sleeve. A sheet carrying thereon an unfixed toner is conveyed as nipped between the fixing sleeve and the pressing roller. The toner on the sheet is melted by the heat of the sleeve itself and exposed to the pressure exerted between the holder and the pressing roller and fixed on the sheet. The holder is provided with a separating member adapted to effect the curvature separation of the sheet from the fixing sleeve. The holder is further provided with a heat-diffusing member made of a material with good thermal conductivity characteristics and non-magnetic properties.