The present invention provides an acrylic thermoplastic resin containing 50 to 95% by mass of a repeating unit (X) derived from a methacrylate monomer represented by the following formula (1), 0.1 to 20% by mass of a repeating unit (Y1) derived from an N-substituted maleimide monomer (a) represented by the following formula (2), and 0.1 to 49.9% by mass of a repeating unit (Y2) derived from an N-substituted maleimide monomer (b) represented by the following formula (3), regarding the total amount of the repeating unit (X), the repeating unit (Y1), and the repeating unit (Y2) as 100% by mass: The absolute value of a photoelastic coefficient (C) of the acrylic thermoplastic resin is not greater than 3.0×10−12 Pa−1. The halogen atom content is less than 0.47% by mass with reference to the mass of the acrylic thermoplastic resin.