PROBLEM TO BE SOLVED: To provide a processing method of a brittle material substrate capable of dividing a brittle material substrate more easily and reliably than heretofore and capable of making an end surface strength of an individual piece after division higher than heretofore.SOLUTION: A method of processing a brittle material substrate, includes: a melt ablation process of condensing a pulse laser beam, irradiating a surface of the brittle material substrate while performing scanning along a predetermined position to be divided in such irradiation conditions that melt ablation occurs on a region irradiated with the pulse laser beam, thereby, forming a groove part along the predetermined position to be divided and, at the same time, forming a crack progressing in a thickness direction of the substrate from the groove part; and a cooling process of cooling the surface of the brittle material substrate having passed through the melting ablation process.
