This paper proposed an on-machine laser deburring method for narrow slits made by laser cutting. Burrs are generally unwanted materials which remain at the cutting edge after machining operations, such as grinding, drilling, milling or turning. A cost necessary to remove burrs becomes a significant portion of the machining costs. In laser cutting, dross removal was significant problem. It is difficult to prevent completely dross from adhering in laser cutting for stainless sheets. In laser cutting for adornments, it is necessary to remove the dross and to chamfer the cutting edges in order not to injure the hand. It is difficult to remove the dross and to chamfer the edges of a narrow slit by machine work or handwork. We irradiated the defocused laser beam to the slits again for these post-processing. To control the depth and width of the removal area, we examined the relationship between the removal area and the deburring conditions. It was clarified that the width and depth of removal area can be controlled by irradiation time and energy fluence.