The characteristics of natural zeolite originated from Kyungbuk, Korea such as X-ray diffraction, cation exchange capacity, ion exchange equilibrium and ion exchange reaction heats were investigated for application to wastewater treatment and other use. Japanese and American natural zeolite samples were also tested to compare with Korean sample. The selectivity coefficient of cation in these materials defined from mass action law does not a constant value as in the case of organic exchange resin.