A heating device for heating a toner image on a sheet via a fixing film, comprising: a substrate disposed such that a first direction of the substrate orthogonal to a conveying direction of the fixing film is longitudinal; characterized by a first heating member (Rin) formed by a first heating resistor (303; 303A, 303B) and a second heating resistor (304; 304A, 304B) that are disposed in a manner substantially symmetrical with respect to a predetermined reference position in a second direction which is parallel to the conveying direction and orthogonal to the first direction of said substrate, said first heating resistor (303; 303A, 303B) and said second heating resistor (304; 304A, 304B) being used for fixing the toner image on the sheet; a second heating member (Rout) formed by a third heating resistor (302; 302A, 302B) and a fourth heating resistor (305; 305A, 305B) that are disposed farther from the reference position in the second direction of said substrate than said first heating member (Rin) and that are arranged in a manner substantially symmetrical with respect to the reference position, said second heating member (Rout) being capable of generating heat independently of said first heating member (Rin), said third heating resistor (302; 302A, 302B) and said fourth heating resistor (305; 305A, 305B) being used for fixing the toner image on the sheet; wherein a plurality of power-supply electrodes (306, 307, 308) connected to said first heating member (Rin) and said second heating member (Rout) are all disposed at one end of said substrate in the longitudinal direction, wherein an end of said first heating member (Rin) and an end of said second heating member (Rout), which are located at the other end of said substrate in the first direction, are arranged on the substrate not to be electrically connected to each other, and wherein in said second heating member (Rout), ends of the third and fourth heating resistors (302; 302A, 302B, 305; 305A, 305B) located at the other end of said substrate in the first direction are arranged to be electrically connected to each other. a substrate disposed such that a first direction of the substrate orthogonal to a conveying direction of the fixing film is longitudinal; characterized by a first heating member (Rin) formed by a first heating resistor (303; 303A, 303B) and a second heating resistor (304; 304A, 304B) that are disposed in a manner substantially symmetrical with respect to a predetermined reference position in a second direction which is parallel to the conveying direction and orthogonal to the first direction of said substrate, said first heating resistor (303; 303A, 303B) and said second heating resistor (304; 304A, 304B) being used for fixing the toner image on the sheet; a second heating member (Rout) formed by a third heating resistor (302; 302A, 302B) and a fourth heating resistor (305; 305A, 305B) that are disposed farther from the reference position in the second direction of said substrate than said first heating member (Rin) and that are arranged in a manner substantially symmetrical with respect to the reference position, said second heating member (Rout) being capable of generating heat independently of said first heating member (Rin), said third heating resistor (302; 302A, 302B) and said fourth heating resistor (305; 305A, 305B) being used for fixing the toner image on the sheet; wherein a plurality of power-supply electrodes (306, 307, 308) connected to said first heating member (Rin) and said second heating member (Rout) are all disposed at one end of said substrate in the longitudinal direction, wherein an end of said first heating member (Rin) and an end of said second heating member (Rout), which are located at the other end of said substrate in the first direction, are arranged on the substrate not to be electrically connected to each other, and wherein in said second heating member (Rout), ends of the third and fourth heating resistors (302; 302A, 302B, 305; 305A, 305B) located at the other end of said substrate in the first direction are arranged to be electrically connected to each other.