To provide a monitor for yarn finish of bobbin in a torchon lace machine, which can detect the minimized left yarn state of each bobbin, emit a warning or stopping signal, stop a machine, and subject to a treatment such as the replacement of the bobbin during a knitting operation of the torchon lace machine, before the yarn on the bobbin is perfectly used up, because a conventional torchon lace machine does not have a means for monitoring the yarn finish of the bobbin.

A sensor capable of monitoring a yarn-wound bobbin is disposed via a supporting means reciprocated on a toothed disk-like member rotated with an independent toothed driving motor, thereby enabling to detect the left yarn of the bobbin on a knitting operation.