Abstract: Disclosed is an apparatus and method for regenerating an etchant solution comprising metal compounds. When a sample of the etchant solution is determined to be of lower etching ability than a predetermined criteria as a result of the monitoring and analyzing three colors(red, green, and blue) of the etchant with color sensors in association with a microprocessor, the etchant solution is reoxidized by the addition of a suitable additive solution. The apparatus and method can regenerate spent etchant solutions containing heavy metals in a semi-permanent manner within the module device without wasting a portion of them, so that, in addition to producing no pollution of the environment, it is economically very favorable with an increase in overall etching efficiency.