The present invention relates to a replication retrovirus vector system comprising thymidine kinase (HSV-TK) gene and cytosine deaminase (CD) gene which make gene transfer to cancer cell tissue for the efficient treatment of cancer. Particularly, the HSV-TK/CD combined self-replicating retrovirus vector system of the present invention characteristically contains both HSV-TK and CD genes; has no worries about losing a therapeutic gene because recombination does not occur in this system during virus infection; and has an excellent stability, and also is able to induce cancer cell death by using the prodrug GCV or 5-FC and can apply a therapeutic gene or a prodrug thereof selectively to such cancer that shows resistance against cancer treatment using either TK or CD, so that this system of the invention can be advantageously used as a pharmaceutical composition for the treatment of cancer.