POLYFUNCTIONAL VINYL AROMATIC COPOLYMER AND METHOD FOR MANUFACTURING SAME, COPOLYMER RUBBER OBTAINED THEREFROM, RUBBER COMPOSITION, RUBBER CROSSLINKED MATERIAL, AND TIRE MEMBER

Provided is a polyfunctional vinyl aromatic copolymer having reactivity and solubility that can be used for manufacturing a copolymer rubber and a copolymer rubber material having processability, strength and homogeneity obtained therefrom. The polyfunctional vinyl aromatic copolymer includes: 0.5 mol% or more and 40 mol% or less of a structural unit (a) derived from a divinyl aromatic compound and 60 mol% or more and 99.5 mol% or less of a structural unit (b) derived from a monovinyl aromatic compound, in which at least some of the structural units (a) are a crosslinked structural unit (a2) represented by the following Formula (2) and a vinyl-group-containing structural unit (a1) represented by the following Formula (1): (in the formulas, R's independently represent an aromatic hydrocarbon group having 6 to 30 carbon atoms), wherein the molar fraction of the crosslinked structural unit (a2) with respect to the structural unit (a) is within a range of 0.05 to 0.50, the molar fraction of the vinyl-group-containing structural unit (a1) with respect to the total amount of the structural units (a) and (b) is within a range of 0.001 to 0.35, the number average molecular weight Mn of the polyfunctional vinyl aromatic copolymer is 1,000 to 50,000, and the molecular weight distribution (Mw/Mn) represented by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is 8.0 or less.