In order to rise the efficiency of measuring the water quality in wetlands , we developed an electrical conductivity (EC) measuring instrument that is exclusive use for wetlands. EC of the ground water is reflected ion concentration , it is used for a rough index of the water quality. From the experiment results in wetlands , we found that EC of peat ground had a close relation to EC of ground water , and that we can roughly grasp differences or a changes of the water quality in wetland using this method.