Industrial development can increase heavy metal pollution in water. Cu metal is an essential heavy metal that is needed in a certain amount by organisms, while in excess the amount is capable of causing toxic properties and environmental pollution. The presence of Cu metal in nature is considered as a pollutant in the concentration range of 0.001 ppm to 0.015 ppm. The electrochemical method can be used for detection of heavy metal. In this work, CPE was modified by electroreduction of 4-carboxyphenyl diazonium by cyclic voltammetry method by contaminating CPE into a 4-CPD solution at potential range -1.5 V to 1,0 V with 100 mV/s scan rate for 3 cycles. The modified of CPE with 4-CPD were characterized using FTIR and SEM-EDX instruments. Analysis of Cu metal using 4-CPD/CPE electrodes showed a good linearity value of 0.9909 with a low detection limit of 0.1635 ppm with the high sensitivity of 21.506 mA ppm cm-2. From these results it can be seen that 4-CPD/CPE can be used as a good Cu metal detector.