For the detection of trace copper to be used in medical diagnosis, a sensitive handmade carbon nanotube paste electrode (PE) was developed using voltammetry. Analytical optimized conditions were found at 0.05 V anodic peak current. In the same conditions, various common electrodes were compared using stripping voltammetry, and the PE was found to be more sharply sensitive than other common electrodes. At optimum conditions, the working ranges of $3{sim}19{mu}gL^{-1}$ were obtained. The relative standard deviation of $70.0{mu}gL^{-1}$ was determined to be 0.117% (n = 15), and the detection limit (S/N) was found to be $0.6{mu}gL^{-1}$ ($9.4{ imes}10^{-9}M$). The results were applied in detecting copper traces in the kidney and the brain cells of fish.