There are provided an anticancer agent degradation method for protecting medical professionals from exposure to an anticancer agent externally scattered in, for example, a safety cabinet or prescription laboratory, during drug preparation or other circumstance, and an anticancer agent degradation apparatus for use with this anticancer agent degradation method. Anticancer agent flyoff in a safety cabinet, etc. is degraded by exploiting an action of ozone-containing air humidified by humidifying means. A relative humidity of humidified ozone-containing air is preferably greater than or equal to 80%. In controlling degradation treatment on the basis of CT values, a difference between expected humidity and measured humidity is reflected in an increment of CT value to understand the progress of anticancer agent degradation properly.