A focus-state detecting device, to which a removable lens unit is mounted, that includes, for example, a focus-state detection unit that detects a focus-adjusted state; a first acquisition unit that acquires information on chromatic aberration; a second acquisition unit that acquires information on spectral characteristics of a subject; a correction unit that corrects information on the focus-adjusted state which has been detected by the focus-state detection unit; and a control unit that repeats operations.