Abstract: A lubricant is supplied from headers of lubricant supply units onto surfaces of back-up rolls at locations spaced from contact positions between a pair of work rolls and a pair of back-up rolls. The headers each include a lubricant spray nozzle for spraying the lubricant under a pressure not lower than 3 kg/cm.sup.2, a header cover for confining the lubricant sprayed from the lubricant spray nozzle, an oil return line for returning the surplus lubricant, and seal members made of flexible material such as rubber. The work rolls are provided with water wiping plates, and the back-up rolls are also provided with water wiping plates. In a work rolls crossing type mill thus arranged, water films of cooling water deposited on the roll surfaces are removed to prevent the cooling water from mixing into the lubricant. Even if the water films are not totally removed, it is possible to surely plate out the lubricant for reliably lubricating between the work rolls and the back-up rolls.