The present invention may provide a plasticizer and a resin composition comprising same, wherein the plasticizer can improve physical properties, such as plasticizing efficiency, migration, tensile strength, elongation rate, stress migration, and light stability, which are required from a sheet prescription when the plasticizer is used as a plasticizer of a resin composition, by making improvement on bad physical properties which have occurred due to structural limits. More specifically, the present invention provides a plasticizer and a method for preparing same, the plasticizer comprising: a terephthalate-based material which is a mixture of three elements; and an epoxy oil, wherein the weight ratio between the terephthalate-based material and the epoxy oil is between 99:1 and 1:99.