Recently, it is necessary to reduce the amount of cutting fluids used in production lines in order to control environmental pollution. The logical step, which can be taken to avoid the environmental problem, is dry machining. However, dry machining is not always acceptable because of unfavorable manufacturing aspects such as decreased tool life and insufficient surface quality. To solve those problems, this study suggests minimal quantity lubrication (MQL) machining which is able to achieve both functions of cooling and lubrication of a cutting fluid and a large amount of air blow. This paper reports the effectiveness of the MQL system in the case of such continous machining as turning particularly when a biodegradable polyol ester is used as a cutting fluid. The lubricating action of this ester oil is also investigated in detail with the aid of surface analysis technics.