To provide a drum preheating device for stabilizing a pressing condition of a side weir to a cooling drum in a twin roll type continuous casting device for manufacturing a thin sheet cast piece.

In this drum preheating method of a twin roll type continuous casting facility, a fixed axis box 3 for fixing a cooling drum axis in a manner not to disposition a cooling drum 1 in an axial direction is installed on an exhaust port side of the cooling water after the cooling drum 1 is cooled. The entire cooling drum is preheated to the temperature equivalent to an average temperature level during casting with the cooling water preheated to the temperature of the same level as the exhausted water temperature till the start of casting in a manner to foresee the temperature rising volume of the cooling water being calculated from the heat releasing volume required for solidification. Furthermore, simultaneously with the start of casting, an operation for lowering the temperature of the cooling water entering the cooling drum 1 is started so as to make the temperature of the exhausted cooling water to be the same level of temperature as the water temperature at the preheating time.