To enable the control of a stable drooping characteristic so that the optimum drooping characteristic constant can be always set.

The method for controlling the speed of the tandem rolling mill is constituted as follows; that is, a control is performed by setting the drooping characteristic constant of a rolling roll drive motor 10 for each motor by a drooping setting instrument 14 so that the speed of each rolling stand becomes lower by a prescribed drooping ratio than a set sped. In this case, the drooping characteristic constant is set by the following formula, DRi=Ci×Vi/(Vp×Di×Ai×Bi) (where DRi: Drooping characteristic constant of (i) stand, Vi: Speed set value of (i) stand, Vp: Speed set value of pivot stand, Di: Roll diameter of (i) stand, Ai: Maximum number of rotations of (i) stand, Bi: Constant set by considering load factor, Ci: Constant set by considering plate size).