To continue level control and continuous molding by, regardless of beginning of supplying molten metal for continuous molding or normal molding, easily and surely coping with sensor damage or erroneous measurement due to abrupt level fluctuation, abnormal molten metal supply or splash-sticking of molten steel.

An attaching device for an eddy current type mold level gauge consists of multiple level gauges 4 and 4' which, assigned on a mold 1 of continuous molding machine, detect the level of molten metal in the mold, a decision means which, based on the mold level signal of the level gauge 4 in measurement, decides possibility of measurement from the change amount of measured value due to sticking of molten steel and then decides possibility of use of the level gauge 4 in measurement, and a switching means which, based on unable-to-use signal from the decision means, switches the level gauge 4 in measurement over to the level gauge 4' in waiting.