To provide a balloon breaker not allowing application of any unreasonable force to wefts when the supplied yarn is to be replaced and capable of controlling a balloon to proper condition at all times.

The balloon breaker 10 is furnished with a first edge 14 to form a circular hole with a part opened and two second edges 18a and 18b continued to the first edge for constituting in cooperation the open part of the circular hole 12. The two second edges extend in the direction going farther than the axis while they are curving in such a way as intersecting mutually in at least two places in the condition apart from each other in the axial direction of the circular hole and also have cut ends.