To enhance the accuracy of inspection to avoid the lowering in the operation rate of a loom.

When a signal-treating circuit substrate 21 containing a defect presence or absence-judging means outputs a malfunction detection signal in a weaving state, an output circuit 39 outputs a loom-stopping signal to a loon control computer Co. A detected position-memorizing circuit 22 constituting a reconfirmation control means C2 memorizes the position of a sensor head 14, namely a detection position, on the output of the malfunction detection signal. The loom control computer Co commands the operation stop of a loom- driving motor M in response to the input of the loom-stopping signal. When the weaving operation of the loom is stopped, the inspection by the travel of the sensor head 14 is carried out. When the sensor head 14 is placed at the detection position and when the malfunction detection signal is outputted, the output circuit 39 outputs an inspection-stopping signal to a scanning control device C1 and simultaneously outputs an alarm signal to an alarm device 25.