To obtain a propylene-ethylene block copolymer having a low modulus and excellent low-temperature characteristics; and to provide a method for producing the block copolymer.

The propylene-ethylene block copolymer has (1) 0.5-50 mol% ethylene content, and (2) ≥95% component eluted at <50°C by a temperature-rising fractionation chromatograph (TREF), satisfies (3) the relation of r1×r2≥0.5 (wherein, r1 is the reactivity ratio of propylene; and r2 is the reactivity ratio of ethylene), and has 0.1-5.0 dl/g intrinsic viscosity.