To provide an abnormality detection device for a thread capable of detecting the abnormal state of the thread independent of the color of the thread and improving the workability of cleaning work.

The abnormality detection device detects the abnormality of a traveling thread Y by an optical means. The abnormality detection circuit is provided with a light emission device 31 to project light to the thread Y, a reflection rod 33 placed at a position opposite to the light emission device 31 interposing the traveling thread Y between these elements, a light receptor 32 placed adjacent and opposite to the reflection rod 33, receiving the light reflected from the thread Y and the reflection rod 33 and converting the reflected light to electric signal, and a controlling means composed of an amplifying circuit 35 to receive the electric signal outputted from the light receptor 32 and detect the presence of the thread Y based on the change of the electric signal, a monitoring timer circuit 36 and an outputting means 37.