Transparent thermoplastic resin and method of preparing the same

A transparent thermoplastic resin, comprising:

• A) 45 to 75% by weight of a graft resin prepared by graft-polymerizing a-1) 40 to 65% by weight of a small-diameter conjugated diene rubber having an average particle diameter of 500 to 1,800 Å, a-2) 22 to 45% by weight of a (meth)acrylic acid alkyl ester compound, a-3) 7 to 18% by weight of an aromatic vinyl compound, and a-4) 0 to 10% by weight of a vinyl cyanide compound;
• and
• B) 25 to 55% by weight of a copolymer resin prepared by copolymerizing b-1) 60 to 80% by weight of a (meth)acrylic acid alkyl ester compound, b-2) 15 to 35% by weight of an aromatic vinyl compound, and b-3) 0 to 10% by weight of a vinyl cyanide compound,
• wherein a weight ratio of a-1) the small-diameter conjugated diene rubber having an average particle diameter of 500 to 1,800 Å to a-2) and b-1) the (meth)acrylic acid alkyl ester compounds (a-1/(a-2+b-1)) is 0.61 to 0.70.