A diagnostic device includes an acquisition unit that acquires sound information, and a display that displays a first analysis result obtained by a time-frequency analysis on the sound information and plural second analysis results obtained by a time-frequency analysis on sound information of an abnormal sound, and that displays the second analysis results in descending order of a possibility presumed to be a cause of the abnormal sound and displays treatment candidates on a screen for inputting a treatment situation of the abnormal sound, based on an order in which the second analysis results have been displayed.