Upon slow operation of a loom, a feed-out motor for a warp beam or a wind-up motor for a surface roller is driven to thereby displace a cloth fell of woven fabric from a normal position toward the fabric, and upon completion of the slow operation, the motor is driven reversely to allow the cloth fell to ressume the normal position. The cloth fell is thereby prevented from being beaten by a reed while protecting woven fabric from generation of weaving bar. Suppression of the weaving bar can also be realized by varying warp tension or a one-shot weft insertion performed from a main weft inserting nozzle while causing auxiliary nozzles to previously produce jets simultaneously or in relays.