To provide a drying device in which an increase in a concentration of an organic solvent in hot air to be supplied to a chamber is suppressed, and which is excellent in the efficiency of energy consumption, and to provide a heat treatment system including the drying device.

A drying part 40 for housing a base material coated with a coating agent including an organic solvent includes a lower hot air spouting part 51 and a lower exhaust box 55. A hot air supply part 53 supplies hot air into the chamber of the drying part 40 from the lower hot air spouting part 51. The hot air spouted to the base material from the lower hot air spouting part 51 is recovered by the lower exhaust box 55, and discharged as exhaust gas including the organic solvent through an exhaust tube 92 to an exhaust part 93. At this time, heat is exchanged between high-temperature exhaust gas and gas taken in from both ends of an outer tube 85, and the temperature of the gas flowing through a space 99 is increased. The temperature-increased gas is supplied from a circulation tube 86 to the hot air supply part 53 and heated, and spouted into the chamber of the drying part 40 from the lower hot air spouting part 51.