To provide a device for cleaning a display part, capable of automatically cleaning and determining the state of the display part after cleaning, with which maintenance is simple, and to provide a display device and a cleaning method.

The brightness of the same display element 16 before and after cleaning is measured by the first brightness measuring instrument 25 and the second brightness measuring instrument 27. If the brightness after the cleaning is not improved by more than a threshold value when compared with the brightness before cleaning, the identification information of the display element is stored in a storage part 68, and after the cleaning of one row of display elements 16, the second cleaning is performed. If there are display elements determined to be without improvement in brightness after the second cleaning, a control part 54 of brightness comparison sends alarm to a main control part 52 about the display elements determined to be without improvement in brightness. The measurement of brightness is performed after drying display elements 16 with a blower 31. A display device 1 is provided with a door 11 and a clerk in charge comes in and goes out to check the maintenance of a cleaning unit 17.