An apparatus for determining the kind of a steel material, comprising: an image pickup device configured for imaging a spark, which is produced when the steel material is ground, continuously a plurality of times; a detection device configured for detecting an alloy spark zone, which corresponds to an alloy spark produced by the grinding of an alloying component contained in the steel material, from each of picked-up images imaged by the image pickup device; a calculation device configured for calculating the total number of alloy spark zones by summing up the number of alloy spark zones of each picked-up image detected by the detection device for all of the picked-up images; and a judgment device for determining that the steel material consists of a low-alloy steel if the total number is not smaller than a first threshold value, and determining that the steel material consists of a carbon steel, being a non-low-alloy steel, if the total number is smaller than the first threshold value, wherein the detection device is configured for performing: first processing in which a spark candidate pixel group (31, 32, 33) consisting of pixels (X1,..., X4) which are continuous with each other along a pixel line and have a density not lower than a second threshold value is detected for one pixel line constituting each of the picked-up images; second processing in which the highest density (Cmax1) of pixels constituting the spark candidate pixel group is detected, and the pixels constituting each of the spark candidate pixel groups are binarized by a third threshold value which is lower than the highest density and larger than the second threshold value, whereby the pixels constituting a spark pixel group are detected from the pixels constituting each of the spark candidate pixel groups; third processing in which a binarized image representing the spark pixel group is prepared by executing the first processing and the second processing for all of the pixel lines constituting each of the picked-up images, and the continuous spark pixel group on the binarized image is recognized as a spark zone corresponding to a spark produced when the steel material is ground; and fourth processing in which the alloy spark zone is detected from the spark zone recognized by the third processing, and wherein the fourth processing comprises: determination processing for determining whether or not the spark zone recognized by the third processing falls under a first determination pattern based on the ratio of the width of an end portion on the front side in the spark scatter direction to the width of an end portion on the rear side in the spark scatter direction in the spark zone recognized by the third processing; and detection processing for detecting the spark zone determined to fall under the first determination pattern by the determination processing as the alloy spark zone. an image pickup device configured for imaging a spark, which is produced when the steel material is ground, continuously a plurality of times; a detection device configured for detecting an alloy spark zone, which corresponds to an alloy spark produced by the grinding of an alloying component contained in the steel material, from each of picked-up images imaged by the image pickup device; a calculation device configured for calculating the total number of alloy spark zones by summing up the number of alloy spark zones of each picked-up image detected by the detection device for all of the picked-up images; and a judgment device for determining that the steel material consists of a low-alloy steel if the total number is not smaller than a first threshold value, and determining that the steel material consists of a carbon steel, being a non-low-alloy steel, if the total number is smaller than the first threshold value, first processing in which a spark candidate pixel group (31, 32, 33) consisting of pixels (X1,..., X4) which are continuous with each other along a pixel line and have a density not lower than a second threshold value is detected for one pixel line constituting each of the picked-up images; second processing in which the highest density (Cmax1) of pixels constituting the spark candidate pixel group is detected, and the pixels constituting each of the spark candidate pixel groups are binarized by a third threshold value which is lower than the highest density and larger than the second threshold value, whereby the pixels constituting a spark pixel group are detected from the pixels constituting each of the spark candidate pixel groups; third processing in which a binarized image representing the spark pixel group is prepared by executing the first processing and the second processing for all of the pixel lines constituting each of the picked-up images, and the continuous spark pixel group on the binarized image is recognized as a spark zone corresponding to a spark produced when the steel material is ground; and fourth processing in which the alloy spark zone is detected from the spark zone recognized by the third processing, and determination processing for determining whether or not the spark zone recognized by the third processing falls under a first determination pattern based on the ratio of the width of an end portion on the front side in the spark scatter direction to the width of an end portion on the rear side in the spark scatter direction in the spark zone recognized by the third processing; and detection processing for detecting the spark zone determined to fall under the first determination pattern by the determination processing as the alloy spark zone.