This operation device (200) is detachably held by a holder (100) provided on an X ray imaging device (1) is for wirelessly operating the X ray imaging device (1) and comprises a control unit (211) that performs a notification operation if a detection is made that prescribed conditions have been met in a state in which the operation device (200) has been removed from the holder (100). As a result various kinds of notifications can be made including notifications for preventing misplacement or loss.