To provide a method for detecting abnormality in a weft detector, which compares the feeler signal, corresponding to luminous energy of incident light while the weft is absent, with the threshold level, and issues an alarm signal when the feeler signal deviates from the threshold level, to secure stable operation.

This method compares the feeler signal S1, corresponding to luminous energy of incident light hitting the light-receiving element while the weft is absent, with the threshold level, and issues an alarm signal S7 when the feeler signal deviates from the threshold level, to detect abnormality in the weft detector 10. It is preferable to find the maximum and minimum levels of the feeler signal S1 corresponding to luminous energy of incident light while the weft is absent, compares the difference between the maximum and minimum levels with the threshold level for alarming, and issues the alarm signal S7 when the difference deviates from the threshold level. It is also preferable that the threshold level for alarming has the same width as the threshold level for the weft detector, which judges whether the weft is present or absent.