A method of continuously casting molten metal has the step of feeding molten metal into a mold to produce a casting continuously while generating an electromagnetic field in the mold by applying a high frequency to the mold. The application of the high frequency is controlled in such a manner that a magnitude of an electromagnetic field which is applied to a solidification shell forming start location of the mold becomes equal to or greater than a minimum required flux density to be applied to the mold. The minimum required flux density is determined according to the following equation: B min = 1130 × t n - 5 ⁢ f × ( t n - 0.05 ) where t n = cos - 1 ⁡ ( v / 2 ⁢ π × f m × a ) / ( π × f m ) Bmin: minimum required flux density (gauss) tn: negative time strip (second) f: frequency in electromagnetic field (kHz) v: casting velocity (m/sec) fm: number of oscillation or frequency of mold (Hz) a: one-way stroke of mold (m).