Abstract: In marking execution mode, after initialization, a scanning control signal based on predetermined marking data and condition data is sent to a scanning head so that a beam spot of a YAG laser beam scans spirally on the interior of a predetermined first black cell in a two-dimensional bar code marking region on the surface of a workpiece W. After the completion of the spiral scanning on the interior of the first black cell, the beam spot skips over from the scanning end point to a scanning start point of a second black cell adjacent to that end point. Then, the interior of the second black cell is also scanned with the beam spot in a unit plotting pattern similar to the above. Afterward, the same spiral scanning as the above is iteratively made on a third and all subsequent black cells. Upon the completion of the spiral scanning on the last black cell, all the marking actions are complete.