PURPOSE: To reduce the reflection of laser light and to improve the convergence by placing a converging lens for converging laser light on a body to be worked in an etching soln. at a prescribed position without leaving a space between the lens and the etching soln.

CONSTITUTION: Laser light L is converged on the surface of a body 2 to be worked in an etching soln. 3 through a converging lens 1. The underside of the lens 1 through which the laser light L passes is in contact with the etching soln. 3, and no space is left between the lens 1 and the soln. 3. The reflection and scattering of laser light L from the surface of the soln. 3 are reduced, the convergence is improved, and the absorption of energy is reduced.