A fixing device (20; 20Y) comprising: a flexible endless belt to move in a predetermined direction to heat and melt a toner image on a recording medium; a pressing rotary member pressed against the belt to form a nip portion to nip and convey the recording medium bearing the toner image as the recording medium passes between the pressing rotary member and the belt; a heater to generate heat; and a heating member (22; 22X; 22Y) fixedly provided inside a loop formed by the belt and facing an inner circumferential surface of the belt, the heating member (22; 22X; 22Y) heated by the heater to heat the belt, the heating member (22; 22X; 22Y) comprising: a primary heating portion (22a; 22Xa; 22Ya) directly heated by the heater; and a secondary heating portion (22b; 22Xb; 22Yb) continuous with and adjacent to the primary heating portion (22a; 22Xa; 22Ya) and heated by heat conducted from the primary heating portion (22a; 22Xa; 22Ya), the primary heating portion (22a; 22Xa; 22Ya) and the secondary heating portion (22b; 22Xb; 22Yb) being provided in a circumferential direction of the heating member (22; 22X; 22Y), the secondary heating portion (22b; 22Xb; 22Yb) having a heat capacity smaller than a heat capacity of the primary heating portion (22a; 22Xa; 22Ya); characterized by a fixed member fixedly provided inside the loop formed by the belt and facing the inner circumferential surface of the belt, the fixed member pressed against the pressing rotary member via the belt to form the nip portion; and a reinforcement member fixedly provided inside the heating member (22; 22X; 22Y) and facing an inner circumferential surface of the heating member (22; 22X; 22Y) to directly or indirectly contact the fixed member to reinforce the fixed member, wherein the heater is provided between the reinforcement member and the primary heating portion (22a; 22Xa; 22Ya) of the heating member (22; 22X; 22Y). a flexible endless belt to move in a predetermined direction to heat and melt a toner image on a recording medium; a pressing rotary member pressed against the belt to form a nip portion to nip and convey the recording medium bearing the toner image as the recording medium passes between the pressing rotary member and the belt; a heater to generate heat; and a heating member (22; 22X; 22Y) fixedly provided inside a loop formed by the belt and facing an inner circumferential surface of the belt, the heating member (22; 22X; 22Y) heated by the heater to heat the belt, the heating member (22; 22X; 22Y) comprising: a primary heating portion (22a; 22Xa; 22Ya) directly heated by the heater; and a secondary heating portion (22b; 22Xb; 22Yb) continuous with and adjacent to the primary heating portion (22a; 22Xa; 22Ya) and heated by heat conducted from the primary heating portion (22a; 22Xa; 22Ya), the primary heating portion (22a; 22Xa; 22Ya) and the secondary heating portion (22b; 22Xb; 22Yb) being provided in a circumferential direction of the heating member (22; 22X; 22Y), the secondary heating portion (22b; 22Xb; 22Yb) having a heat capacity smaller than a heat capacity of the primary heating portion (22a; 22Xa; 22Ya); characterized by a fixed member fixedly provided inside the loop formed by the belt and facing the inner circumferential surface of the belt, the fixed member pressed against the pressing rotary member via the belt to form the nip portion; and a reinforcement member fixedly provided inside the heating member (22; 22X; 22Y) and facing an inner circumferential surface of the heating member (22; 22X; 22Y) to directly or indirectly contact the fixed member to reinforce the fixed member, a primary heating portion (22a; 22Xa; 22Ya) directly heated by the heater; and a secondary heating portion (22b; 22Xb; 22Yb) continuous with and adjacent to the primary heating portion (22a; 22Xa; 22Ya) and heated by heat conducted from the primary heating portion (22a; 22Xa; 22Ya), the primary heating portion (22a; 22Xa; 22Ya) and the secondary heating portion (22b; 22Xb; 22Yb) being provided in a circumferential direction of the heating member (22; 22X; 22Y), the secondary heating portion (22b; 22Xb; 22Yb) having a heat capacity smaller than a heat capacity of the primary heating portion (22a; 22Xa; 22Ya); characterized by a fixed member fixedly provided inside the loop formed by the belt and facing the inner circumferential surface of the belt, the fixed member pressed against the pressing rotary member via the belt to form the nip portion; and a reinforcement member fixedly provided inside the heating member (22; 22X; 22Y) and facing an inner circumferential surface of the heating member (22; 22X; 22Y) to directly or indirectly contact the fixed member to reinforce the fixed member, wherein the heater is provided between the reinforcement member and the primary heating portion (22a; 22Xa; 22Ya) of the heating member (22; 22X; 22Y).