A device and method for measuring concentration of etchant, the device comprises a concentration measuring mechanism and an acid mist elimination mechanism connected with the concentration measuring mechanism, the acid mist elimination mechanism is configured to eliminate acid mist inside the concentration measuring mechanism, and the concentration measuring mechanism is configured to receive etchant in real time, measure absorbance of each kind of acid of the etchant in a non-acid mist environment, and calculate concentration of each kind of acid of the etchant according to the absorbance. It can overcome the interference of the acid mist on concentration measurement of the acid of the acid mixture etchant. In this way, the concentration of each kind of acid of the acid mixture etchant can be online measured rapidly and accurately, and the desiccative gas can be recycled, which achieves the effect of resource conservation.