To provide an abnormality detector for the motion transmission mechanism of a loom, capable of accurately detecting the abnormality of the motion transmission mechanism by disposing an abnormality-detecting means for distinguishing the interlocking state between a main shaft and a driven shaft.

This abnormality detector for the motion transmission mechanism of a loom in obtained by disposing a rotation detector 11 for detecting the rotation of a driven shaft 32, a standard angle-setting device 12 for setting the standard angle θo of a main shaft in response to a check signal Sc from the rotation sensor 11, and an abnormality-detecting means 21 for distinguishing an interlocking state between the main shaft MS and the driven shaft 32 on the basis of the check signal Sc. When the generation phase of the check signal Sc on the standard angle θo exceeds a phase tolerance Δθo, the abnormality- detecting means 21 outputs an abnormal signal Sa to an outer member.