The present invention relates to a block copolymer that contains a polymer block A containing a farnesene-derived monomer unit (a1) and a random copolymer block B containing a C12 or lower conjugated diene-derived monomer unit (b1) and an aromatic vinyl compound-derived monomer unit (b2), the block copolymer having a ratio by mass of the polymer block A to the random copolymer block B (A/B) of 30/70 to 0.5/99.5, a content of the aromatic vinyl compound-derived monomer unit (b2) in the random copolymer block B of 1 to 50% by mass, and a weight average molecular weight (Mw) of 100,000 to 5,000,000.