PURPOSE: To improve the efficiency in roiling and to make a product at low cost by superposing plural metal sheets, grinding the joining face as occasion demands and executing cold rolling by coating a rolling lubrication oil on a roil from the outlet side of a rolling mill.

CONSTITUTION: Plural metal sheets A, B are superposed, the joining face thereof is ground in advance, if necessary, and they are led into the work roll 3, 3' of a rolling mill. In this case, a rolling oil is projected a little on the roll from the rolling oil feeding pipe 4 of the rolling mill outlet side and nozzles 3, 3'. The rolling oil is thinly spread uniformly on the roll surface by being squeezed by the gap of work roll 1, 1' and backup roll 2, 2', lubricating the space between the metal sheet A, B prior to joining and work roll 1, 1'. The rolling is executed at low rolling load when cold rolling is executed in this state due to no foreign matter existed between the sheet A, B. The rolling efficiency is thus improved and the product cost is reduced owing to the saving in consuming power.