In order to measure the minute amount of Cu(II) in our environment, cyclic voltammetry (CV) and square-wave stripping voltammetry (SWSV) were performed for a trace copper assay using bismuth immobilized on a carbon nanotube paste electrode. An analytical working range of 30 to $240{mu}g/L$ Cu(II) was obtained for CV and SWSV. The SWSV precision obtained was 0.47 % (n = 15) RSD in $30.0{mu}g/L$ Cu(II). The detection limit obtained was 3.1 ng/L Cu(II) using SWSV, while the CV yielded the nano-range detection limit through the pre-concentration step. By using this research method, Cu(II) value could be determined in the urine of human sample and in the brain of fish sample. This research can be effectively applied to other cases of measuring minute amount of Cu(II) in living organisms.