The present invention has an object to provide a vaccinia virus expressing a foreign gene and capable of killing cancer cells, and a cancer therapy drug comprising the vaccinia virus. The present invention relates to a vaccinia virus, wherein a suicide gene as a foreign gene selected from the group consisting of cytosine deaminase (CD) gene, uracil phosphoribosyltransferase (UPRT) gene, and herpes simplex virus thymidine kinase (HSV-tk) gene is introduced.
