The present invention provides a method for prominently inhibiting the production in fungi of mycotoxin, which has serious effects on health of humans and other animals, and provides a mycotoxin production inhibitor. Mycotoxin content such as deoxinivalenol (DON) in harvested crops can be reduced without a correlation with the control effects against fungi by spraying a fungicide containing a benzimidazole-type fungicidal compound such as thiophanate-methyl as an active ingredient onto food crops such as wheat, barley, and the like. Concomitant use of the benzimidazole-type fungicidal compound and a sterol biosynthesis inhibitor (SBI agent) such as tebuconazole can further enhance the effect.