A rotor-fixing resin composition for use for forming a fixing member comprised by a rotor, wherein the rotor comprises a rotor core fixed and installed on a rotating shaft in which a plurality of hole portions are provided along the peripheral portion of the rotating shaft, a magnet inserted in the hole portions, and the fixing member that fixes the magnet and wherein the fixing member is provided in a separation portion between the hole portion and the magnet, the rotor-fixing resin composition comprising: an epoxy resin-containing thermosetting resin; a curing agent; a silane coupling agent; and silica as an inorganic filler, wherein the inorganic filler is subjected to a surface treatment using the silane coupling agent in which the silane coupling agent and the inorganic filler are mixed, and the mixture is subjected to an aging treatment under the condition of 20±5°C for 7 days or more to couple the silane coupling agent to the surface of the inorganic filler, wherein the epoxy resin includes at least one selected from the group consisting of a biphenyl-based epoxy resin, a phenolaralkyl-based epoxy resin, a phenol novolac-based epoxy resin, an orthocresol novolac-based epoxy resin, a bisphenol-based epoxy resin, a bisnaphthol-based epoxy resin, a dicyclopentadiene-based epoxy resin, a dihydroanthracenediol-based epoxy resin, and a triphenylmethane-based epoxy resin, wherein the curing agent includes at least one phenolic resin selected from the group consisting of a novolac-based phenolic resin, a phenolaralkyl resin, a naphtholbased phenolic resin, and a phenolic resin formed by reacting hydroxybenzaldehyde, formaldehyde and phenol, wherein the amount of the inorganic filler is equal to or more than 50% by mass and equal to or less than 93% by mass based on 100% by mass of the total amount of the rotor-fixing resin composition, wherein the rotor-fixing resin composition is in a powder form, a granule form or a tablet form, a tensile elongation at break-a at 120°C is 0.1% or higher and 1.7% or lower, wherein an elastic modulus of the cured product at 120°C is 0.8 × 10 4 MPa or higher, wherein an elastic modulus of the cured product at 25°C is 1.4 × 10 4 MPa or higher, wherein the tensile elongation at break-a is calculated by the following Equation, wherein Xo mm represents the whole length of the test piece before a tensile test and X 1 mm represents the whole length of the test piece after the tensile test, wherein the tensile elongation at break-a is obtained by subjecting a test piece to a tensile test pursuant to JIS K7162 under conditions of a temperature of 120°C, a test load of 20 MPa and 100 hours by using a creep testing machine and a strain gauge for the measurement of the tensile elongation at break: Tensile elongation at break − a = X 1 mm − X 0 mm / X 0 mm × 100, and the test piece is a cured product produced by subjecting the rotor-fixing resin composition to curing by heating at 175 °C for 4 hours, and molding to a dumbbell shape pursuant to JIS K7162. an epoxy resin-containing thermosetting resin; a curing agent; a silane coupling agent; and silica as an inorganic filler, wherein the inorganic filler is subjected to a surface treatment using the silane coupling agent in which the silane coupling agent and the inorganic filler are mixed, and the mixture is subjected to an aging treatment under the condition of 20±5°C for 7 days or more to couple the silane coupling agent to the surface of the inorganic filler, wherein the epoxy resin includes at least one selected from the group consisting of a biphenyl-based epoxy resin, a phenolaralkyl-based epoxy resin, a phenol novolac-based epoxy resin, an orthocresol novolac-based epoxy resin, a bisphenol-based epoxy resin, a bisnaphthol-based epoxy resin, a dicyclopentadiene-based epoxy resin, a dihydroanthracenediol-based epoxy resin, and a triphenylmethane-based epoxy resin, wherein the curing agent includes at least one phenolic resin selected from the group consisting of a novolac-based phenolic resin, a phenolaralkyl resin, a naphtholbased phenolic resin, and a phenolic resin formed by reacting hydroxybenzaldehyde, formaldehyde and phenol, wherein the amount of the inorganic filler is equal to or more than 50% by mass and equal to or less than 93% by mass based on 100% by mass of the total amount of the rotor-fixing resin composition, wherein the rotor-fixing resin composition is in a powder form, a granule form or a tablet form, a tensile elongation at break-a at 120°C is 0.1% or higher and 1.7% or lower, wherein an elastic modulus of the cured product at 120°C is 0.8 × 10 4 MPa or higher, wherein an elastic modulus of the cured product at 25°C is 1.4 × 10 4 MPa or higher, wherein the tensile elongation at break-a is calculated by the following Equation, wherein Xo mm represents the whole length of the test piece before a tensile test and X 1 mm represents the whole length of the test piece after the tensile test, wherein the tensile elongation at break-a is obtained by subjecting a test piece to a tensile test pursuant to JIS K7162 under conditions of a temperature of 120°C, a test load of 20 MPa and 100 hours by using a creep testing machine and a strain gauge for the measurement of the tensile elongation at break: Tensile elongation at break − a = X 1 mm − X 0 mm / X 0 mm × 100, and the test piece is a cured product produced by subjecting the rotor-fixing resin composition to curing by heating at 175 °C for 4 hours, and molding to a dumbbell shape pursuant to JIS K7162.