A fixing device comprising: a fixing belt having an endless shape; a pressure member configured to press the fixing belt; a nip formation member disposed inside a loop of the fixing belt and configured to contact the pressure member via the fixing belt; a heater configured to heat the fixing belt; and a support disposed inside the loop of the fixing belt and configured to support the nip formation member, the nip formation member including: a first nip forming portion configured to contact the pressure member via the fixing belt to form a first fixing nip; a second nip forming portion disposed downstream from the first nip forming portion in a direction (C1, C2) of conveyance of a recording medium and configured to contact the pressure member via the fixing belt to form a second fixing nip; an inflection portion at which a direction of extension of the nip formation member changes; and a supported portion disposed downstream from the first nip forming portion in the direction of conveyance of the recording medium, the supported portion supported by and in contact with the support, wherein the inflection portion is disposed at a position of the supported portion or a position downstream from the supported portion in the direction of conveyance of the recording medium, wherein the second nip forming portion is disposed downstream from the inflection portion and characterized in that the fixing device further comprises means for changing the pressing force of the pressure member to the fixing belt and in that a posture of the second nip forming portion relative to the first nip forming portion is variable with a change in a pressing force between the nip formation member and the pressure member. a fixing belt having an endless shape; a pressure member configured to press the fixing belt; a nip formation member disposed inside a loop of the fixing belt and configured to contact the pressure member via the fixing belt; a heater configured to heat the fixing belt; and a support disposed inside the loop of the fixing belt and configured to support the nip formation member, the nip formation member including: a first nip forming portion configured to contact the pressure member via the fixing belt to form a first fixing nip; a second nip forming portion disposed downstream from the first nip forming portion in a direction (C1, C2) of conveyance of a recording medium and configured to contact the pressure member via the fixing belt to form a second fixing nip; an inflection portion at which a direction of extension of the nip formation member changes; and a supported portion disposed downstream from the first nip forming portion in the direction of conveyance of the recording medium, the supported portion supported by and in contact with the support, wherein the inflection portion is disposed at a position of the supported portion or a position downstream from the supported portion in the direction of conveyance of the recording medium, wherein the second nip forming portion is disposed downstream from the inflection portion and characterized in that the fixing device further comprises means for changing the pressing force of the pressure member to the fixing belt and in that a posture of the second nip forming portion relative to the first nip forming portion is variable with a change in a pressing force between the nip formation member and the pressure member. a first nip forming portion configured to contact the pressure member via the fixing belt to form a first fixing nip; a second nip forming portion disposed downstream from the first nip forming portion in a direction (C1, C2) of conveyance of a recording medium and configured to contact the pressure member via the fixing belt to form a second fixing nip; an inflection portion at which a direction of extension of the nip formation member changes; and a supported portion disposed downstream from the first nip forming portion in the direction of conveyance of the recording medium, the supported portion supported by and in contact with the support, wherein the inflection portion is disposed at a position of the supported portion or a position downstream from the supported portion in the direction of conveyance of the recording medium, wherein the second nip forming portion is disposed downstream from the inflection portion and characterized in that the fixing device further comprises means for changing the pressing force of the pressure member to the fixing belt and in that a posture of the second nip forming portion relative to the first nip forming portion is variable with a change in a pressing force between the nip formation member and the pressure member.