The solidification state of a slab during continuous casting is estimated by means of a heat transmission model that uses heat flux, which is based at least on the cooling conditions of the secondary cooling, and the temperature distribution in the width direction of the slab is measured with a thermometer at a previously established measurement position in the longitudinal direction of the slab, which is the direction in which the slab is drawn out. The heat flux distribution of the heat flux in the width direction of the slab is corrected so that the estimated temperature at the measurement position, which is estimated with the heat-transmission model, and the temperature distribution in the width direction of the slab, measured with the temperature distribution measurement means, coincide, thereby making it possible to estimate the final solidification position and the final solidification shape in continuous casting more accurately.