The present invention relates to an oncolytic virus improved in safety and anticancer effect and a use thereof. The oncolytic virus improved in safety and anticancer effect of the present invention is obtained by inserting an HSV-TK fragment-encoding gene into a TK gene region to delete TK of Vaccinia virus. In addition, the oncolytic virus of the present invention expresses an HSV-TK fragment to phosphorylate GCV so that cancer cells infected with the oncolytic virus and even their neighboring cancer cells can be killed. In addition, GCV is also involved in the suppression of viral proliferation and thus can control side effects caused by a virus even upon the administration of a high dose of the virus. Furthermore, an anticancer effect is increased even though the number of viral particles is reduced due to the suppression of GCV against virus proliferation. Therefore, the oncolytic virus improved in safety and anticancer effect of the present invention can be effectively used for the treatment of cancer.