A fixing device characterized by comprising: a tubular belt holder extending in an axial direction thereof; a rotatable, flexible fuser belt looped into a generally cylindrical configuration around the belt holder extending in the axial direction of the belt holder, the tubular belt holder retaining the fuser belt in shape as the belt rotates in a circumferential direction of the belt holder; a contact member having a central axis thereof extending in the axial direction of the belt holder, accommodated in the belt holder inside the loop of the fuser belt; a pressure member having a central axis thereof extending in the axial direction, disposed opposite the belt holder with the fuser belt interposed between the contact member and the pressure member, the pressure member pressing against the contact member through the fuser belt to form a fixing nip through which a recording medium travels in a conveyance direction under heat and pressure; and a heater disposed adjacent to the belt holder to heat directly or indirectly a predetermined circumferential portion of the fuser belt upstream from the fixing nip in the circumferential direction, the belt holder including a generally semi-cylindrical section to face the heated circumferential portion of the fuser belt, whose radius is approximately equal to a radius of the fuser belt in the generally cylindrical configuration of the fuser belt, characterised in that the center of the generally semi-cylindrical section is positioned upstream, in the conveyance direction, from a trans-axial plane containing the central axes of the contact member and the pressure member. a tubular belt holder extending in an axial direction thereof; a rotatable, flexible fuser belt looped into a generally cylindrical configuration around the belt holder extending in the axial direction of the belt holder, the tubular belt holder retaining the fuser belt in shape as the belt rotates in a circumferential direction of the belt holder; a contact member having a central axis thereof extending in the axial direction of the belt holder, accommodated in the belt holder inside the loop of the fuser belt; a pressure member having a central axis thereof extending in the axial direction, disposed opposite the belt holder with the fuser belt interposed between the contact member and the pressure member, the pressure member pressing against the contact member through the fuser belt to form a fixing nip through which a recording medium travels in a conveyance direction under heat and pressure; and a heater disposed adjacent to the belt holder to heat directly or indirectly a predetermined circumferential portion of the fuser belt upstream from the fixing nip in the circumferential direction, the belt holder including a generally semi-cylindrical section to face the heated circumferential portion of the fuser belt, whose radius is approximately equal to a radius of the fuser belt in the generally cylindrical configuration of the fuser belt, characterised in that the center of the generally semi-cylindrical section is positioned upstream, in the conveyance direction, from a trans-axial plane containing the central axes of the contact member and the pressure member.