To overcome the problem of a prior art such that the amount of etching varies depending on the position of a workpiece in a treatment bath and hence it is difficult to obtain the high-quality and pure workpiece when performing etching treatment to the surface of the workpiece such as a semiconductor wafer or a liquid crystal substrate.

A number of flat workpiece 2 are retained sideways with a fixed interval at space in the treatment bath 1. At the same time, a treatment liquid supply tube 5 whose tip section is blocked, whose inner diameter decreases in a tapered shape toward the tip from the root, and in which the tube 5 has a number of nozzles 6 pointed to the direction of the workpiece 2 on the tube wall, is arranged at the lower portion of the retention axis center of the workpiece 2 and in parallel with the retention axis center, thus composing the treatment device.