An apparatus 1 for determining a kind of a steel material detects a spark pixel from a color picked-up image 2 of a spark 19 produced when a steel material 18 is ground, and detects a pixel, in which the density of any one color component for judgment selected from among RGB color components is low, as a low-density pixel from the spark pixels. The apparatus 1 determines that the steel material is a steel material consisting of the high-strength steel if the ratio of the total number of low-density pixels to the total number of spark pixels is not lower than a threshold value for judgment, and determines that the steel material is a steel material consisting of the ordinary steel if the ratio is lower than the threshold value for judgment.