A drying device for drying a recording medium is provided. The drying device includes a plurality of heating roller units independently detachable from the drying device. The heating roller units includes at least one upstream heating roller unit disposed upstream relative to a conveyance direction of the recording medium and at least two downstream heating roller units disposed downstream relative to the conveyance direction of the recording medium. Each upstream heating roller unit includes an upstream heating roller, two upstream temperature detectors, and two upstream controllers. The upstream heating roller includes two upstream heat sources having different heating areas. The two upstream temperature detectors are disposed at respective end parts of the upstream heating roller, to detect temperatures of the respective upstream heat sources to output signals. The two upstream controllers control the respective upstream heat sources based on the respective signals from the respective upstream temperature detectors.