To provide a metal processing oil composition exhibiting excellent processing performance such as cutting and grinding in the case of applying to a minimal quantity lubrication method.

The metal processing oil composition is produced by compounding a fatty acid ester with an -olefin, wherein the fatty acid ester contains 2-6 ester bonds in the molecule, the number of carbon atoms of the -olefin is 6-18, and the compounded amount of the -olefin is 0.5-20 mass% based on the whole composition.