Method of supplying lubrication oil in cold rolling

A method of feeding lubrication oil for supplying an emulsion comprised of a lubrication oil and heated water mixed together to an inlet side of a rolling stand in cold rolling of a metal sheet, comprising storing two types of lubrication oils of different compositions and the lubrication oils and additives in separate tanks, setting in advance two mixing ratios of a first mixing ratio and second mixing ratio in accordance with the friction coefficient for said two types of lubrication oil or a lubrication oil and additive, supplying a first emulsion produced by said first mixing ratio to the inlet side of the rolling stand, increasing the emulsion supplying rate to reduce the friction coefficient when the estimated friction coefficient during rolling is larger than a target friction coefficient, switching to a second emulsion produced by said second mixing ratio and supplying the second emulsion to the inlet side of the rolling stand when the increase of said emulsion supplying rate reduces the friction coefficient, and switching said second emulsion to said first emulsion to reduce the emulsion supplying rate and supplying the first emulsion to the inlet side of the rolling stand when the estimated friction coefficient during rolling is smaller than the target friction coefficient.