A laser processing method which can securely prevent particles from attaching to chips obtained by cutting a planar object is provided. When applying a stress to an object to be processed 1 through an expandable tape 23, forming materials of the object 1 (the object 1 formed with molten processed regions 13, semiconductor chips 25 obtained by cutting the object 1, particles produced from cut sections of the semiconductor chips 25, and the like) are irradiated with soft x-rays. As a consequence, the particles produced from the cut sections of the semiconductor chips 25 obtained by cutting the object 1 fall on the expandable tape 23 without dispersing randomly. This can securely prevent the particles from attaching to the semiconductor chips 25 obtained by cutting the object 1.