Disclosed is a transparent plastic sheet obtained by co-polymerizing 100 parts by weight of methyl methacrylate with 0.1 to 2.0 parts by weight of methacrylic acid and 0.1 to 1.5 parts by weight of glycidyl methacrylate, and having a thickness of not greater than 4 inches, wherein the angular deviation satisfies specified conditions according to the thickness of the sheet and wherein the degree of swelling is not greater than 2.50. This transparent plastic sheet shows neither coloring nor sink marks on the surface, has excellent craze resistance and low long-term water absorption percentage, and is hence suitable for use as an aircraft windshield.