A fixing device (B) comprising: a cylindrical film ; a heater contacting an inner surface of said film and including an electrode portion for supplying electric power to said heater , and a lubricant (G) is applied in a region where said heater contacts said film ; and a supporting member for supporting a surface of said heater opposite from a surface of said heater where said heater contacts said film ; wherein an image on a recording material (P) is heated by heat of said film and is fixed on the recording material (P), characterized by further comprising: a sealing member contacting a surface of said heater where said electrode portion of said heater is provided, said sealing member being provided at a position closer to a center of said heater than said electrode portion is, wherein said electrode portion is provided outside an end portion of said film with respect to a longitudinal direction of said film at an end portion of said heater with respect to a longitudinal direction of said heater , wherein the heater is a plate heater , wherein said sealing member includes an engaging portion engaging with an end portion of said supporting member with respect to a widthwise direction of said heater and a cantilever contact portion contacting the surface of said heater where said electrode portion is provided. a cylindrical film ; a heater contacting an inner surface of said film and including an electrode portion for supplying electric power to said heater , and a lubricant (G) is applied in a region where said heater contacts said film ; and a supporting member for supporting a surface of said heater opposite from a surface of said heater where said heater contacts said film ; wherein an image on a recording material (P) is heated by heat of said film and is fixed on the recording material (P), characterized by further comprising: a sealing member contacting a surface of said heater where said electrode portion of said heater is provided, said sealing member being provided at a position closer to a center of said heater than said electrode portion is, wherein said electrode portion is provided outside an end portion of said film with respect to a longitudinal direction of said film at an end portion of said heater with respect to a longitudinal direction of said heater , wherein the heater is a plate heater , wherein said sealing member includes an engaging portion engaging with an end portion of said supporting member with respect to a widthwise direction of said heater and a cantilever contact portion contacting the surface of said heater where said electrode portion is provided. a sealing member contacting a surface of said heater where said electrode portion of said heater is provided, said sealing member being provided at a position closer to a center of said heater than said electrode portion is, wherein said electrode portion is provided outside an end portion of said film with respect to a longitudinal direction of said film at an end portion of said heater with respect to a longitudinal direction of said heater , wherein the heater is a plate heater , wherein said sealing member includes an engaging portion engaging with an end portion of said supporting member with respect to a widthwise direction of said heater and a cantilever contact portion contacting the surface of said heater where said electrode portion is provided. <EOS>