Provided are a polyolefin resin having two crystallization temperatures, a resin composition including the polyolefin resin, an encapsulant film, a method for manufacturing the encapsulant for an optoelectronic device, and an optoelectronic device, in which the encapsulant having high light transmittance and low haze value can be provided even under the condition of low lamination, and the resin composition including the polyolefin resin can be used for manufacturing various encapsulants for an optoelectronic device, thereby providing excellent adhesive strength with the front substrate and back sheet included in the device, especially, a long-term adhesion property and improved heat resistance.