Provided are a vinyl chloride-based resin formed by polymerization of vinyl chloride-based small seed particles having an average particle diameter range of 0.15 μm to 0.5 μm prepared by emulsion polymerization and vinyl chloride-based large seed particles having an average particle diameter range of 0.51 μm to 0.8 μm prepared by micro-suspension polymerization, in which a content ratio (weight ratio) of the large seed particles to the small seed particles is in a range of 1 to 2, and a method of preparing the vinyl chloride-based resin. Excellent low viscosity characteristics of the vinyl chloride resin at high and low shear rates may be obtained by controlling the particle size of the small seed prepared by emulsion polymerization.