A fixing device comprising: an endless fixing belt rotatably supported by a belt holding component; a pressure roller disposed to press an outer peripheral surface of the fixing belt and cause rotation of the fixing belt when the pressure roller is rotated; a nip formation member disposed on an inner peripheral surface of the fixing belt to form a nip portion in the fixing belt between the nip formation member and the pressure roller when the fixing belt is pressed by the pressure roller; and a heating unit to heat the fixing belt; a support member disposed to support the nip formation member on the inner peripheral surface of the fixing belt without contacting the fixing belt, wherein the support member comprises a parallel portion that supports the nip formation member and extends parallel to a sheet transport direction in the nip portion, and a rise portion that extends from the parallel portion in a direction drawn apart from the nip portion, and the rise portion is inclined to the parallel portion such that an inclination direction of the rise portion is substantially parallel to a virtual straight line connecting a center of rotation of the fixing belt and an inlet point of the nip portion or falls within a range of rotational angles of ± 15°by which the virtual straight line is rotated around the center of rotation of the fixing belt, characterised in that the support member further comprises a reflection surface disposed thereon, or between the support member and the heating unit, configured to reflect radiant heat emitted from the heating unit; wherein the reflection surface is arranged such that the radiant heat emitted from the heating unit is reflected to the fixing belt by a part or all of the reflection surface in directions toward portions of the fixing device other than the heating unit. an endless fixing belt rotatably supported by a belt holding component; a pressure roller disposed to press an outer peripheral surface of the fixing belt and cause rotation of the fixing belt when the pressure roller is rotated; a nip formation member disposed on an inner peripheral surface of the fixing belt to form a nip portion in the fixing belt between the nip formation member and the pressure roller when the fixing belt is pressed by the pressure roller; and a heating unit to heat the fixing belt; a support member disposed to support the nip formation member on the inner peripheral surface of the fixing belt without contacting the fixing belt, wherein the support member comprises a parallel portion that supports the nip formation member and extends parallel to a sheet transport direction in the nip portion, and a rise portion that extends from the parallel portion in a direction drawn apart from the nip portion, and the rise portion is inclined to the parallel portion such that an inclination direction of the rise portion is substantially parallel to a virtual straight line connecting a center of rotation of the fixing belt and an inlet point of the nip portion or falls within a range of rotational angles of ± 15°by which the virtual straight line is rotated around the center of rotation of the fixing belt, characterised in that the support member further comprises a reflection surface disposed thereon, or between the support member and the heating unit, configured to reflect radiant heat emitted from the heating unit; wherein the reflection surface is arranged such that the radiant heat emitted from the heating unit is reflected to the fixing belt by a part or all of the reflection surface in directions toward portions of the fixing device other than the heating unit.