Tool-work thermo-electromotive force (E.M.F.) is very important signal because it is regarded as the evidence of direct cutting phenomenon at the cutting position. Our aim is to carry out in-process monitoring of tool wear under intermittent cutting conditions. We examined the relation between E.M.F. and tool flank wear to explore the possibility of in-process tool wear detection using E.M.F. Waveform variations in E.M.F. signals corresponding to tool flank wear were observed at the starting position of cut. To determine the cause of these waveform variations, the electric current was also measured and the electric resistance between the tool and work piece were calculated using Ohm's law. It is found that the change in the tool-work electric resistance corresponds to the progression of the tool flank wear. By monitoring this tool-work electric resistance, it is possible to conduct in-process detection of tool flank wear.