A method for producing a halohydantoin compound according to the present invention includes the steps of: (a) providing, in a dryer, a composition containing (i) at least one component selected from the group consisting of water, an organic solvent, and elemental halogen and (ii) a halohydantoin compound; and (b) drying the composition under reduced pressure in the dryer, the reduced pressure being reduced to a pressure lower than atmospheric pressure while introducing an inert gas from an outside source into the dryer.