PURPOSE: To control the water concentration in drying liquid in the bottom of a tank at a predetermined concentration or less in a vapor dryer which condenses vapor dried on the surface of a material to be treated to dry it, uses a plurality of separate film modules to separate to remove moisture from condensed liquid to be reused.

CONSTITUTION: This vapor dryer comprises a treating tank 1 for condensing to dry the vapor of drying liquid, and a separate film module 10 formed of a film for selectively permeating water. The tank 1 has a vapor generator 2 of the liquid, a drying space 4 for disposing a material W to be treated, a first receiver 5 for collecting generated condensed liquid at the lower part, a cooling coil 6 and a second receiver 7 for collecting the condensed liquid generated by cooling. Automatic valves 18 are placed at the channel 11 of the condensed liquid of the first receiver and the channel 12 of the second receiver.