An object of the present invention is to provide a block copolymer having the excellent improving characteristics. Specifically, the block copolymer is a hydrogenated block copolymer capable of obtaining a molded product, as a polyolefin based resin composition, having excellent physical property balance between impact resistance, in particular, low temperature impact resistance and rigidity, and molding processability, and further, capable of providing, as a viscous adhesive composition, a composition having an excellent balance between adhesion characteristics such as adhesive power and retentivity, and having excellent melt viscosity stability under heating at a high temperature. The block copolymer is a hydrogenation product of a block copolymer having at least one polymer block mainly comprising a vinyl aromatic hydrocarbon and at least one polymer block mainly comprising a conjugate diene compound, and having a vinyl bonding amount V (%) based on the conjugate diene compound of from not less than 37% to less than 70%, wherein (a) the total hydrogenation ratio H (%) of the unsaturated double bond based on the conjugate diene compound satisfies the following relational formulae: V