A process for preparing a propylene polymer composition having excellent rigidity, heat resistance and impact resistance comprising conducting multistage polymerization including a step (a) for preparing a propylene (co)polymer (A), a step (b) for preparing a propylene-olefin copolymer (B) and a step (c) for preparing an ethylene-olefin copolymer (C) in the presence of (I) a transition metal compound and (II) a compound activating the transition metal compound (I), in which the steps (a), (b) and (c) are carried out in any order, each of the second and subsequent stage polymerizations is carried out in the presence of a polymer or polymers obtained by the preceding stage or stages, respectively, and the resulting propylene polymer composition contains the propylene (co)polymer (A) in an amount of 20 to 90% by weight, the propylene-olefin copolymer (B) in an amount of 5 to 75% by weight and the ethylene-olefin copolymer (C) in an amount of 5 to 75% by weight, and has MFR, as measured at 230.degree. C. under a load of 2.16 kg, of 0.01 to 500 g/10 min.