Disclosed are a data encryption apparatus and a data encryption method using an encryption key based on puncturing of a generator matrix. Bit values located in a column at a specific point are punctured from a generator matrix of a Reed-Muller (RM) code and thereafter, encryption of a message is performed through a public key generated by using the punctured generator matrix to defend an attack from a third party based on a structure of the RM code by change of the structure of the generator matrix, thereby solving security vulnerability caused as the existing McEliece encryption system uses the generator matrix of the RM code having a special structure as it is.