An electrochemical measurement cell that enables the measurement of the rest potential, potentiostatic polarization, and anodic polarization curve of an electrode under wet etching was developed under wet etching by spray. The Cu electrode was fabricated by screen printing to simulate a printed circuit board. Its cross-section was analyzed using optical microscopy after electrochemical measurements. Measurements of the Cu electrode rest potential were conducted under wet etching with different flow rates. The Cu electrode rest potential was shifted to noble potential when the flow rate of spray was high under wet etching. Results show that the Cu electrode dissolution was explained by the mixed potential theory. The Cu electrode cross-section after the potentiostatic polarization showed that the cross-section shape was controlled by the polarization potential. Furthermore, the current densities of the potentiostatic polarizations showed good agreement with that of the anodic polarization curves. The details of the Cu electrode dissolution behavior under wet etching by spray using the electrochemical measurement cell are discussed.