The present invention relates to an olefin-based polymer satisfying conditions as follow: (1) a melt index (MI, 190° C., 2.16 kg load conditions) is from 0.1 g/10 min to 10.0 g/10 min, (2) a density (d) is from 0.860 g/cc to 0.880 g/cc, and (3) T(90)−T(50)≤50 and T(95)−T(90)≥10 are satisfied when measured by a differential scanning calorimetry precise measurement method (SSA). The olefin-based polymer according to the present invention is a low-density olefin-based polymer introducing a highly crystalline region and showing high mechanical rigidity.