1. A source code equivalence verification device that verifies equivalence between an original source code and a source code after refactoring execution, comprising: a source code input unit that receives a non-refactored source code and a refactored source code; a refactoring pattern input unit that receives refactoring pattern information of the source code; a source code information generating unit that performs lexical analysis and syntax analysis on each of the non-refactored source code and the refactored source code, converts the non-refactored source code and the refactored source code into structure graphs, and generates non-refactored source code information and refactored source code information; a normalizing unit that normalizes the non-refactored source code information and the refactored source code information with reference to normalization information defined for refactoring pattern information, and generates normalized non-refactored source code information and normalized refactored source code information; a structure comparing unit that compares a structure of the normalized non-refactored source code information with a structure of the normalized refactored source code information; a symbolic execution unit that performs symbolic execution on the normalized non-refactored source code information and the normalized refactored source code information; and an equivalence determining unit that compares symbolic execution results obtained by the symbolic execution unit, and determines equivalence between the non-refactored source code and the refactored source code.