The present invention provides an opening-and-closing mechanism capable of reducing a falling momentum due to gravitational force of a lid that is opened and closed past the top in the perpendicular direction and easily raising the lid against the gravitational force. The opening-and-closing mechanism includes two supporting members (7, 9) and an intermediate member (15) disposed so as to be relatively rotatable about a rotation axis; a first damper (11R), disposed between a first one of the supporting members (9) and the intermediate member (15), for generating resistance against rotation during relative rotation of the two supporting members (7, 9) in one direction; a second damper (11L), disposed between a second one of the supporting members (7) and the intermediate member (15), for generating resistance against rotation during relative rotation of the two supporting members (7, 9) in another direction; and rotation-restricting portions (29R, 29L) for restricting relative rotation ranges of the two supporting members (7, 9) and the intermediate member (15).