A control portion executes a measuring mode and generates a value for adjusting a pressurizing mechanism reflecting a difference of pressurizing conditions of a longitudinal center part and a longitudinal end part of a nip portion. The measuring mode is a mode of detecting temperatures of the nip portion by temperature detecting elements in a process of changing temperature of the nip portion heated by a heater and of generating control information based on detected results. The control information is generated in response to a difference of temperature increase amounts of the temperature detecting elements in a predetermined time in the process of increasing the temperature of the nip portion. The control portion adjusts the pressurizing mechanism based on the control value obtained in the measuring mode after executing a process of heating a recording medium in succession of the process of increasing the temperature of the nip portion.