The present invention relates to an olefin-based polymer, which has (1) a density (d) ranging from 0.850 g/cc to 0.865 g/cc, (2) a melt index (MI, 190° C., 2.16 kg load conditions) ranging from 0.1 g/10 min to 3.0 g/10 min, (3) a melt temperature (Tm) of 10° C. to 100° C., and (4) a hardness (H, Shore A), the density (d) and the melt temperature (Tm) satisfying Equation 1, and Equation 2 or 3. The olefin-based polymer according to the present invention has low hardness and improved foaming properties, and exhibits improved impact strength at compounding.