A drying device includes a conveying unit, a hot air blowing unit, a passage forming unit, and an adjusting unit. The conveying unit conveys a medium to which a liquid is discharged from a discharging head. The hot air blowing unit includes a blowing unit that blows air, and a heating unit that heats air. The passage forming unit forms, between the hot air blowing unit and a region on a conveying unit conveyance path, a circulation path through which air blown from the hot air blowing unit is circulated. The adjusting unit adjusts a ratio between inside air circulating through the circulation path and outside air that is introduced into the circulation path. If a temperature increase condition is established, the adjusting unit increases a ratio of the inside air. If a temperature decrease condition is established, the adjusting unit increases a ratio of the outside air.