The present invention relates to an olefin-based polymer exhibiting a single peak when analyzed by gel permeation chromatography (GPC), and having three elution temperatures Te1, Te2 and Te3 when measuring temperature rising elution fractionation (TREF) at a temperature ranging from −20° C. to 120° C. Accordingly, the olefin-based polymer having excellent mechanical strength, and in particular, significantly improved impact strength is provided.