A modified olefin resin obtained by performing an extrusion reaction of a resin composition comprising: a polyolefin resin having a first crystallization temperature of 20°C to 35°C and a second crystallization temperature of 35°C to 75°C that is higher than the first crystallization temperature, wherein the polyolefin resin has one melting temperature and satisfies the following Equation 1: 10 ° C ≤ Tc 2 − Tc 1 − Tm − Tc 2 ≤ 20 ° C wherein, in Equation 1, Tc 1 represents the first crystallization temperature, Tc 2 represents the second crystallization temperature, and Tm represents the melting temperature, and wherein the crystallization temperatures are confirmed through analyzing the peaks of a cooling curve of a heat flow measured by differential scanning calorimetry while cooling the polymers from 200°C to -150°C at a rate of 10°C/min; an unsaturated silane compound which is a compound represented by the following Chemical Formula 5: [Chemical Formula 5] DSiR 10 p R 11 (3-p) where, in Chemical Formula 5, D represents alkenyl that is bound to a silicon atom, R 10 represents a hydroxyl group, halogen, an amine group, or -R 12 R 13, which is bound to a silicon atom, R 12 represents an oxygen or sulfur atom, R 13 represents an alkyl group, an aryl group, or an acyl group, R 11 represents hydrogen, an alkyl group, an aryl group, or an aralkyl group, which is bound to a silicon atom, and p represents an integer of 1 to 3; a radical initiator; and an amino silane compound which is a compound represented by the following Chemical Formula 6: [Chemical Formula 6] SiR 14 q R 15 (4-q) where, in Chemical Formula 6, R 14 represents -(CH 2) r NR 16 R 17 which is bound to a silicon atom, R 16 and R 17 each independently represent hydrogen or R 18 NH 2, which is bound to a nitrogen atom, R 18 represents alkylene, R 15 represents halogen, an amine group, -R 19 R 20, or -R 20, which is bound to a silicon atom, R 19 represents an oxygen or sulfur atom, R 20 represents hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, q represents an integer of 1 to 4, and r represents an integer of 0 or more. a polyolefin resin having a first crystallization temperature of 20°C to 35°C and a second crystallization temperature of 35°C to 75°C that is higher than the first crystallization temperature, wherein the polyolefin resin has one melting temperature and satisfies the following Equation 1: 10 ° C ≤ Tc 2 − Tc 1 − Tm − Tc 2 ≤ 20 ° C wherein, in Equation 1, Tc 1 represents the first crystallization temperature, Tc 2 represents the second crystallization temperature, and Tm represents the melting temperature, and wherein the crystallization temperatures are confirmed through analyzing the peaks of a cooling curve of a heat flow measured by differential scanning calorimetry while cooling the polymers from 200°C to -150°C at a rate of 10°C/min; an unsaturated silane compound which is a compound represented by the following Chemical Formula 5: [Chemical Formula 5] DSiR 10 p R 11 (3-p) where, in Chemical Formula 5, D represents alkenyl that is bound to a silicon atom, R 10 represents a hydroxyl group, halogen, an amine group, or -R 12 R 13, which is bound to a silicon atom, R 12 represents an oxygen or sulfur atom, R 13 represents an alkyl group, an aryl group, or an acyl group, R 11 represents hydrogen, an alkyl group, an aryl group, or an aralkyl group, which is bound to a silicon atom, and p represents an integer of 1 to 3; a radical initiator; and an amino silane compound which is a compound represented by the following Chemical Formula 6: [Chemical Formula 6] SiR 14 q R 15 (4-q) where, in Chemical Formula 6, R 14 represents -(CH 2) r NR 16 R 17 which is bound to a silicon atom, R 16 and R 17 each independently represent hydrogen or R 18 NH 2, which is bound to a nitrogen atom, R 18 represents alkylene, R 15 represents halogen, an amine group, -R 19 R 20, or -R 20, which is bound to a silicon atom, R 19 represents an oxygen or sulfur atom, R 20 represents hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, q represents an integer of 1 to 4, and r represents an integer of 0 or more.