A fusing apparatus and method for an image forming apparatus comprise a housing, a first roller mounted in the housing, a second roller rotated in contact with the first roller, a heater movably mounted in at least one of the first and the second rollers and comprising a first heater and a second heater, a first power supplying terminal and a second power supplying terminal movably supported in the housing, and a pair of connection units movably supported in the housing to connect the respective heater terminals to the corresponding power supplying terminals. The power supplying terminals and the connection units have a predetermined gap with an outer surface of the housing, such that when the housing expands in a lengthwise or horizontal direction of the heater, the outer surface of the housing tightly contacts with at least one of the heater terminals, the power supplying terminals and the connection units, thereby fixing or securing the heater in the housing.