Provided is an opening-and-closing mechanism that can be latched at a predetermined opening angle, wherein the latching can be disengaged with a small force in the opening direction whereas the latching is gradually disengaged in the closing direction. An opening-and-closing mechanism includes first and second supporting members disposed relatively rotatable around a rotary axis; a plurality of protruding portions provided on the first supporting member; and a plurality of depressed portions provided on the second supporting member and engaged with the plurality of protruding portions, wherein, when the first and second supporting members are in a plurality of predetermined relative alignments, some of the plurality of protruding portions and some of the plurality of depressed portions are engaged, and wherein forces required for disengaging the protruding portions and the depressed portions by rotating at least one of the first and second supporting members differ first and second rotation directions.