A method for producing an olefin block polymer, the method includes: polymerizing olefin using a polymerization catalyst (X), a polymerization catalyst (Y), and an organometallic compound (C) having an atom of any of Groups 2, 12, and 13 of the periodic table of the elements, the organometallic compound (C) excluding an activating co-catalyst agent (B), wherein: the polymerization catalyst (X) is formed by bringing a transition metal compound (A-X) represented by a general formula (1-X) into contact with an activating co-catalyst agent (B); and the polymerization catalyst (Y) is formed by bringing a transition metal compound (A-Y) represented by a general formula (1-Y) into contact with the activating co-catalyst agent (B). [Chem. 2] (MLaXbEc)n  (1-Y)