The present invention relates to a transparent thermoplastic resin. More particularly, the present invention relates to a transparent thermoplastic resin, including a random copolymerization block prepared by polymerizing 50 to 80% by weight of an aromatic vinyl compound, 10 to 30% by weight of a vinyl cyanide compound, and 0 to 15% by weight of (meth)acrylic acid alkyl ester; and an aromatic vinyl compound block prepared by polymerizing 1 to 10% by weight of an aromatic vinyl compound, a transparent thermoplastic resin composition including the transparent thermoplastic resin, and methods of preparing the aromatic vinyl compound and transparent thermoplastic resin.