(Meth) acrylic resin composition, its production method and the optical member

A (meth)acrylic resin composition is obtained by means of a method which involves: obtaining a polymerization reaction solution by dissolving a block copolymer (B), which has a polymer block (a) comprising an alkyl ester (meth)acrylate unit and a polymer block (b) comprising a conjugated diene compound unit, in a monomer mixture (a') containing 50 to 100 mass% of a methyl methacrylate; and polymerizing the monomer mixture (a') once the moisture content within the polymerization reaction solution reaches 1000 ppm or less.