An opening apparatus that opens continuously conveyed bags with a gas supplied by nozzles. A plurality of nozzles having conical head sections and discharge openings at the tip ends are attached to a rotation transmitting member with equal spaces in between, and this rotation transmitting member is caused to revolve at a constant speed while maintaining a horizontal attitude by means of a parallel link mechanism. The nozzles revolve at a constant speed on a circular track in a vertical plane along the conveying direction of bags with the discharge openings consistently facing the bags. When the nozzles are at the lower point on the circular track, the head sections enter into the bags that are being conveyed at a constant speed, and a gas is caused to jet into the bags from the discharged openings, thus spread-opening the bags.