Disclosed is a control method of a ventilation apparatus, the method including: a determination step in which measured outdoor temperature and humidity and the measured indoor temperature and humidity are equal to or greater than a set temperature and a set humidity; and a drying operation step in which, when the outdoor temperature and humidity and the indoor temperature and humidity, reach the set temperature and the set humidity, a first desiccant heat exchanger and a second heat exchanger operate in a dry mode, wherein the first desiccant heat exchanger is provided in a first common passage, through which indoor space air or outdoor space air flows, to absorb or desorb moisture, and the second desiccant heat exchanger is provided in a second common passage, which is separate from the first common passage, and through which indoor air or outdoor air flows, to absorb or desorb moisture in air.