The present invention provides a method for slicing a single crystal, wherein the single crystal is sliced by irradiating a portion to be sliced with an ultra short pulse laser beam while supplying a gas containing gaseous molecules or radicals that react with atoms constituting the single crystal to become stable gaseous molecules in the vicinity of the portion under slicing. Thus, there is provided a method for slicing a single crystal by using a laser processing, in which a single crystal is processed while obtaining a good sliced surface and markedly reducing a slicing loss.