An image forming apparatus includes a fusing apparatus including a fusing member; a heating unit heating the fusing member; temperature detecting units detecting temperatures of the fusing member and a pressing member; and the pressing member forming a fusing nip with the fusing member for fusing an un-fused image on a recording medium onto a recording medium. The image forming apparatus further includes a heating power determining unit determining heating power of the fusing apparatus by measuring a time or a gradient of time versus temperature before the temperature of the fusing member reaches a reload temperature after power is turned on. The image forming apparatus includes a control unit performing a feed permission control or a CPM down control depending on the heating power of the fusing apparatus and the number of sheets of the recording medium to be passed through the fusing apparatus.