A fixing device comprising: a rotatable fixing member configured to heat a recording medium carrying a yet-to-be-fixed image thereon; a rotatable pressing member configured to come into contact with the fixing member to form a nip between the fixing member and the pressing member ; a heat source configured to heat the fixing member ; a first temperature detecting unit configured to detect a temperature of the fixing member ; characterized by a second temperature detecting unit configured to detect a temperature of the pressing member ; and a temperature control unit configured to electrify the heat source at a predetermined control period based on pieces of temperature information received from the first temperature detecting unit and the second temperature detecting unit , respectively, wherein the predetermined control period or a gap between recording media is set so that T1 + T2 = C × N is satisfied, where T1 denotes a time from when a leading end of the recording medium reaches the nip to when a trailing end of the recording medium passes through the nip, T2 denotes a time corresponding to the gap between the recording media, C denotes the predetermined control period, and N denotes a positive integer; and heat generated by the heat source is supplied to the recording medium in synchronization with a timing at which the recording medium enters the nip, a correction amount is added to an electrification time in each predetermined control period and the correction amount is changed with a predetermined rate in each control period based on the piece of temperature information of the pressing member before feeding of the recording medium is started, and the correction amount is changed depending on a basis weight of the recording medium. a rotatable fixing member configured to heat a recording medium carrying a yet-to-be-fixed image thereon; a rotatable pressing member configured to come into contact with the fixing member to form a nip between the fixing member and the pressing member ; a heat source configured to heat the fixing member ; a first temperature detecting unit configured to detect a temperature of the fixing member ; characterized by a second temperature detecting unit configured to detect a temperature of the pressing member ; and a temperature control unit configured to electrify the heat source at a predetermined control period based on pieces of temperature information received from the first temperature detecting unit and the second temperature detecting unit , respectively, wherein the predetermined control period or a gap between recording media is set so that T1 + T2 = C × N is satisfied, where T1 denotes a time from when a leading end of the recording medium reaches the nip to when a trailing end of the recording medium passes through the nip, T2 denotes a time corresponding to the gap between the recording media, C denotes the predetermined control period, and N denotes a positive integer; and heat generated by the heat source is supplied to the recording medium in synchronization with a timing at which the recording medium enters the nip, a correction amount is added to an electrification time in each predetermined control period and the correction amount is changed with a predetermined rate in each control period based on the piece of temperature information of the pressing member before feeding of the recording medium is started, and the correction amount is changed depending on a basis weight of the recording medium. <EOS>