It is an object to provide a block copolymer composition for a viscous adhesive, which will be a viscous adhesive composition excellent in balance of the adhesive properties such as tack strength and tackiness, having a low melt viscosity, and excellent solubility, coating properties, ejection stability, and surface skin quality. The block copolymer composition for a viscous adhesive having: a component (a) in an amount of 50 mass % or more and 90 mass % or less; and a component (b) in an amount of 10 mass % or more and 50 mass % or less; a content of the vinyl aromatic monomer unit being 25 to 50 mass %; a viscosity of the 15 mass % toluene solution being 10 to 40 mPa·s; and a number average molecular weight ratio of the component (b) to the component (a) being 2.0 to 4.0.