Abstract: Provided is an oncolytic virus having both improved safety and productivity. Provided are: a conditionally replicating vaccinia virus which lacks the functions of a vaccinia virus growth factor (VGF), an extracellular signal-regulated kinase (ERK) activation protein, and a ribonucleotide reductase (RNR), is not replicated in a normal cell, is selectively replicable in a proliferative cell, and has improved safety; and a conditionally replicating vaccinia virus which lacks the functions of a VGF, an ERK activation protein, and an RNR, is not replicated in a normal cell, is selectively replicable in a proliferative cell, and has improved safety and productivity, and in which a gene encoding an extracellular enveloped virus (EEV)-related protein is substituted with a gene corresponding to another vaccinia virus strain having a high EEV-producing ability.