The present invention provides a preventive and/or therapeutic agent for sleeping disorder, which comprises, as an active ingredient, a dibenzo[b,e]oxepine derivative represented by formula (I): (wherein R.sup.1, R.sup.2, and R.sup.3 may be the same or different and each represents a hydrogen atom or lower alkyl, and m and n may be the same or different and each represents an integer of 1 to 4) or a pharmaceutically acceptable salt thereof.