It was found that cupric ion selective electrode, which was prepared by mixing CuS and $Ag_2S$ with the ratio four to one and PVC, was hard and durable. The response potentials were reproducible and linear in the range from 1.0 ${ imes}$ $10^{-1}M$ to 1.0 ${ imes}$ $10^{-5}M$ copper (II) solution and its slope was 25.0 mV per decade concentration at $298^{circ}K$, slightly different from Nernstian slope. The copper (II) indicating electrode was applied in precipitation titration of 1.0 ${ imes}$ $10^{-2} M Cu(II)$ sample solution containing proper amounts $NaNO_3$ with 0.1 M NaOH standard solution. Also, this electrode could be used in complex titration of Zn(II), Mg(II), Ca(II) with EDTA and stability constant of EDTA complex of Ca(II) and Mg(II) was calculated by using known Cu-$EDTA^{2-}$ stability constant.