The present invention provides a herpes virus in which a non-essential gene for replication is inactivated More particularly, the present invention provides a herpes virus in which a non-essential gene for replication present in a UL or US region is inactivated. More preferably, the non-essential gene for replication contains US3 or UL56. The herpes virus may be preferably a herpes simplex virus, and more preferably herpes simplex virus 1 or herpes simplex virus 2. The present invention provides a method, composition and use for treating various diseases or disorders including tumor and infectious diseases. The present invention also provides a method, composition and use for activating a prodrug.