A method for producing an α-olefin/(meth)acrylic acid ester copolymer, wherein a metal complex obtained by reacting a compound represented by the following general formula or with a transition metal compound containing a transition metal selected from nickel or palladium having a structure of the following general formula, is used: wherein, in the general formulae to, R 3 to R 11, E 1 and X 1 are as follows: X 1 represents oxygen or sulfur; E 1 represents phosphorus, arsenic or antimony; R 3 and R 4 each independently represent a hydrocarbon group having 5 to 30 carbon atoms and optionally containing at least one kind selected from the group consisting of a heteroatom and at least one heteroatom-containing group, wherein the hydrocarbon group is a linear alkyl group, an acyclic alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group or an alkylaryl group, and wherein a heteroatom-containing group is at least one kind selected from the group consisting of an alkoxy group, an aryloxy group, an acyl group, an ester group, a dialkylamino group, an amide group, a thioalkoxy group, a thioaryloxy group, a dialkylphosphino group, a selenyl group, a trialkylsilyl group, a dialkylarylsilyl group, an alkyldiarylsilyl group, a fluoroalkyl group, a fluoroaryl group, an alkyl boron group and an aryl boron group; R 5 to R 8 each independently represent a hydrogen atom, a halogen, a hydrocarbon group having 1 to 30 carbon atoms and optionally containing a heteroatom, OR 2,CO 2 R 2, CO 2 M', C N(R 1) 2, C R 2, SR 2, SO 2 R 2, OSO 2 R 2, P (OR 2) 2-y (R 1) y, CN, NHR 2, N(R 2) 2, Si(OR 1) 3-x (R 1) x, OSi(OR 1) 3-x (R 1) x, NO 2, SO 3 M', PO 3 M' 2, P (OR 2) 2 M' or an epoxy-containing group, where R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms; R 2 represents a hydrocarbon group having 1 to 20 carbon atoms; M' represents an alkali metal, ammonium, quaternary ammonium or phosphonium; x represents an integer of from 0 to 3; and y represents an integer of from 0 to 2; R 9 to R 11 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and optionally containing a heteroatom, and wherein, in the general formula, Z represents a hydrogen atom or a leaving group, and m represents a valence of Z. X 1 represents oxygen or sulfur; E 1 represents phosphorus, arsenic or antimony; R 3 and R 4 each independently represent a hydrocarbon group having 5 to 30 carbon atoms and optionally containing at least one kind selected from the group consisting of a heteroatom and at least one heteroatom-containing group, wherein the hydrocarbon group is a linear alkyl group, an acyclic alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group or an alkylaryl group, and wherein a heteroatom-containing group is at least one kind selected from the group consisting of an alkoxy group, an aryloxy group, an acyl group, an ester group, a dialkylamino group, an amide group, a thioalkoxy group, a thioaryloxy group, a dialkylphosphino group, a selenyl group, a trialkylsilyl group, a dialkylarylsilyl group, an alkyldiarylsilyl group, a fluoroalkyl group, a fluoroaryl group, an alkyl boron group and an aryl boron group; R 5 to R 8 each independently represent a hydrogen atom, a halogen, a hydrocarbon group having 1 to 30 carbon atoms and optionally containing a heteroatom, OR 2,CO 2 R 2, CO 2 M', C N(R 1) 2, C R 2, SR 2, SO 2 R 2, OSO 2 R 2, P (OR 2) 2-y (R 1) y, CN, NHR 2, N(R 2) 2, Si(OR 1) 3-x (R 1) x, OSi(OR 1) 3-x (R 1) x, NO 2, SO 3 M', PO 3 M' 2, P (OR 2) 2 M' or an epoxy-containing group, where R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms; R 2 represents a hydrocarbon group having 1 to 20 carbon atoms; M' represents an alkali metal, ammonium, quaternary ammonium or phosphonium; x represents an integer of from 0 to 3; and y represents an integer of from 0 to 2; R 9 to R 11 each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and optionally containing a heteroatom, and wherein, in the general formula, Z represents a hydrogen atom or a leaving group, and m represents a valence of Z.