A method for dividing a semiconductor wafer into chips according to the present invention is a method for dividing a semiconductor wafer into a large number of semiconductor chips, the semiconductor wafer having a semiconductor layer formed on a substrate. A first method includes the step of forming a blast-resistant mask on a surface of the semiconductor wafer, the blast-resistant mask having a pattern for leaving a grid-like exposed portion as it is and the step of blasting a fine particular blast material to thereby form dividing grooves reaching a predetermined depth of the substrate in the grid-like exposed portion. A second method includes the step of forming first dividing grooves in a surface of the semiconductor wafer in which the semiconductor layer is formed, by dicing, etching or blasting, so that the first dividing grooves have a relatively narrow groove width, and the step of forming second dividing grooves in a surface of the semiconductor wafer in which the semiconductor layer is not formed by dicing, and in positions corresponding to the first dividing grooves, so that the second dividing grooves have a relatively wide groove width.