An image forming apparatus that is configured to form a toner image on an image carrier, to transfer the toner image (t) to a recording sheet and to fix the toner image (t) on the recording sheet with a fixing device comprising a rotatable heating member having a plurality of heaters (h1, h2) embedded therein and a rotatable pressing member, the heating member and the pressing member opposed to each other to form a nip portion, which a fixing process is performed while the recording sheet is passing through so that the toner image (t) is heated and pressed to be fixed on the recording sheet, the image forming apparatus comprising: a power source for electrifying the plurality of heaters (h1, h2); a temperature detector for detecting a temperature of the heating member; and a controller for controlling the power source, wherein the plurality of heaters (h1, h2) includes a first heater that generates a greater amount of heat from its central portion with respect to a direction of a rotation axis of the heating member than from its end portions with respect to the direction of the rotation axis of the heating member; wherein the controller controls the power source such that at least one of the plurality of heaters (h1, h2) is controlled to be turned on and off based on a difference between the temperature detected by the temperature detector and a target temperature of the heating member so that the temperature of the heating member can become the target temperature; and wherein the controller controls the power source such that only the first heater is turned on and off during a printing operation, wherein the plurality of heaters (h1, h2) includes a second heater that generates a greater amount of heat from its end portions with respect to the direction of rotation axis of the heating member than the amount of heat generated from the end portions of the first heater with respect to the direction of rotation axis of the heating member; and wherein the controller controls the power source such that only the second heater is controlled to be turned on and off during a standby state of not performing printing, wherein the controller calculates a first time when the recording sheet with the toner image (t) thereon passes through the nip portion to be subjected to the fixing process and determines a second time to stop controlling the second heater and to start controlling the first heater in a transition from the standby state to the printing operation based on the calculated time when the recording sheet passes through the nip portion in such a manner to ensure the fixing process be conducted on the recording sheet, the second time is when the leading edge of the recording sheet comes into the nip portion, a predetermined time before the time when the leading edge of the recording sheet comes into the nip portion or a time immediately after the time when the leading edge of the recording sheet comes into the nip portion, so that the fixing process is conducted on the recording sheet. a power source for electrifying the plurality of heaters (h1, h2); a temperature detector for detecting a temperature of the heating member; and a controller for controlling the power source, wherein the plurality of heaters (h1, h2) includes a first heater that generates a greater amount of heat from its central portion with respect to a direction of a rotation axis of the heating member than from its end portions with respect to the direction of the rotation axis of the heating member; wherein the controller controls the power source such that at least one of the plurality of heaters (h1, h2) is controlled to be turned on and off based on a difference between the temperature detected by the temperature detector and a target temperature of the heating member so that the temperature of the heating member can become the target temperature; and wherein the controller controls the power source such that only the first heater is turned on and off during a printing operation, wherein the plurality of heaters (h1, h2) includes a second heater that generates a greater amount of heat from its end portions with respect to the direction of rotation axis of the heating member than the amount of heat generated from the end portions of the first heater with respect to the direction of rotation axis of the heating member; and wherein the controller controls the power source such that only the second heater is controlled to be turned on and off during a standby state of not performing printing, wherein the controller calculates a first time when the recording sheet with the toner image (t) thereon passes through the nip portion to be subjected to the fixing process and determines a second time to stop controlling the second heater and to start controlling the first heater in a transition from the standby state to the printing operation based on the calculated time when the recording sheet passes through the nip portion in such a manner to ensure the fixing process be conducted on the recording sheet, the second time is when the leading edge of the recording sheet comes into the nip portion, a predetermined time before the time when the leading edge of the recording sheet comes into the nip portion or a time immediately after the time when the leading edge of the recording sheet comes into the nip portion, so that the fixing process is conducted on the recording sheet.