A block copolymer is obtained by anionic polymerization, includes two or more polymer blocks A miscible with each other, and at least one (meth)acrylic ester polymer block B immiscible with the polymer blocks A, has a ratio [Mn(Amax) / Mn(Amin)] of 2 or more, wherein the ratio [Mn(Amax) / Mn(Amin)] is the ratio of the largest number average molecular weight [Mn(Amax)] to the smallest number average molecular weight [Mn(Amin)] among the polymer blocks A, has at least one block bonding including polymer block Amax-polymer block B-polymer block Amin, and has a total content of the polymer blocks A ranging from 20 wt % to 45 wt % based on the total mass of the block copolymer. This invention provides block copolymers having two or more polymer blocks A miscible with each other and at least one (meth)acrylic ester polymer block B immiscible with the polymer blocks A and exhibiting satisfactory flexibility, melt fluidity, moldability, coatability, mechanical properties, and other properties. The block copolymers of the present invention can yield molded articles having reduced anisotropy and surface stickiness and excellent mechanical properties and pressure-sensitive adhesive compositions having excellent adhesive properties.