To provide a catalyst for manufacturing stably and efficiently a crystalline propylene component having a higher melting point and an ethylene--olefin copolymer component having a higher ethylene content, and to provide a method for manufacturing a propylene/ethylene--olefin-based block copolymer using the same.

The -olefin polymerization catalyst components include (A) at least two transition metal compounds in the Periodic Table group 4 selected from components (A-1) and (A-2) respectively, and (B) at least one compound selected from a group consisting of (B-1) an aluminiumoxy compound, (B-2) an ionic compound or Lewis acid capable of converting into a cation by reacting with the above transition metal compounds (A), (B-3) a solid acid particulate and (B-4) an ion-exchangeable layer silicate. A method for manufacturing a propylenic block copolymer comprises using the same.