PURPOSE: To improve working efficiency, by inserting a semiconductor device into a measuring socket, performing electric inspection with a measuring part which is connected to the socket, oscillating a laser with the semiconductor device being inserted in the socket, and writing a mark on the semiconductor device through a disk for masking.

CONSTITUTION: A semiconductor device is inserted into a measuring socket 8. When a desired signal is obtained through a measuring part 9 which is electrically connected to said socket, a signal is imparted to an oscillating part 1 which is provided at the upper part of the measuring part 9, and laser oscillation is performed. Then, the laser light is condensed. The condensed light is projected on a disk 5 for masking. The laser light is introduced on the upper part of a package for the semiconductor device 7, and marking is performed. Thus, the time required forming from the inspecting step to the marking step is not required, and the working efficiency is improved.