A method for preventing a breakout of molten steel in a solidifying shell in a mold in continuous casting, the method comprising: periodically collecting time-domain pressure data about a change in pressure of a cylinder of a mold oscillator from a pressure sensor (110a, 110b) mounted onto the cylinder; dividing the pressure data collected in a unit time into first and second period data, one of the first and second period data being collected from one sampling interval before the present time to the beginning of the unit time and the respective other of the first and second period data being collected from the present time to one sampling interval after the beginning of the unit time; converting respective period data to frequency-domain data; and analyzing power spectra of the converted data, the power spectra being a correlation with respect to a variation in power according to frequencies; calculating a time delay coefficient associated with a delay in signal by analyzing pressure data collected in a unit time with respect to a cross correlation between the first and second period data using a conventional cross correlation analysis algorithm, the time delay coefficient quantifying a time delay of oscillations of the mold by an increased contact force between the solidifying shell and the mold; and comparing amplitudes of respective frequencies of the first and second period data obtained via the analysis of the power spectra, and controlling a casting speed when the amplitude of the frequency of present time period data of the first and second period data is reduced from that of previous time period data of the first and second period data by a reference ratio or more and the calculated time delay coefficient is not less than a reference value. periodically collecting time-domain pressure data about a change in pressure of a cylinder of a mold oscillator from a pressure sensor (110a, 110b) mounted onto the cylinder; dividing the pressure data collected in a unit time into first and second period data, one of the first and second period data being collected from one sampling interval before the present time to the beginning of the unit time and the respective other of the first and second period data being collected from the present time to one sampling interval after the beginning of the unit time; converting respective period data to frequency-domain data; and analyzing power spectra of the converted data, the power spectra being a correlation with respect to a variation in power according to frequencies; calculating a time delay coefficient associated with a delay in signal by analyzing pressure data collected in a unit time with respect to a cross correlation between the first and second period data using a conventional cross correlation analysis algorithm, the time delay coefficient quantifying a time delay of oscillations of the mold by an increased contact force between the solidifying shell and the mold; and comparing amplitudes of respective frequencies of the first and second period data obtained via the analysis of the power spectra, and controlling a casting speed when the amplitude of the frequency of present time period data of the first and second period data is reduced from that of previous time period data of the first and second period data by a reference ratio or more and the calculated time delay coefficient is not less than a reference value.