A modified acrylic block copolymer is obtained by a method comprising subjecting a block copolymer (C) to a reaction with an amine compound, wherein the block copolymer comprises a polymer block (A) comprising a (meth)acrylic acid ester unit (a) and a polymer block (B′) comprising a (meth)acrylic acid ester unit (b′), the (meth)acrylic acid ester unit (a) is structurally different from the (meth)acrylic acid ester unit (b′), thereby partly or entirely converting the (meth)acrylic acid ester unit (b′) into at least one selected from the group consisting of an N-substituted (meth)acrylamide unit (d), a (meth)acrylic acid unit (c), and an N-substituted bis((meth)acryl)amide unit (e).