Abstract: A roll cooling device for a rolling mill having rolls comprises cooling water guide plates each having a curved surface along a circumferential direction of rolls, the cooling water guide plates being provided close to the rolls, cooling water supply headers for supplying cooling water to cooling water passages defined by the cooling water guide plate and the rolls, water discharge headers for discharging the cooling water, supplied by the water supply headers, from the cooling water passages, support members supporting the cooling water guide plates, and curvature adjusting members for changing curvature of the guide plates in accordance with a diameter of the rolls. A thickness of the guide plate is increased from each edge portion to a central portion of the guide plate in the circumferential direction of the roll. In the case where the roll diameter is largely changed, the clearance between the guide plate and the roll is kept suitably, thereby sufficiently cool the rolls.