Soxhlet-type leaching experiments were carried out for 200 days and the leaching solutions analyzed by inductively coupled plasma spectroscopy and atomic absorption spectroscopy. The data of the solution analysis and the results of our previous study on the surface layers revealed the fact that elements in the waste glass were classified into three groups and were released into solution in accordance with the following mechanisms: Group I contained sodium, cesium, potassium, boron, and molybdenum; the release of the group I elements was controlled by diffusion and decomposition processes in the glass. Group II contained manganese, iron, nickel, zirconium, yttrium, lanthanum, cerium, neodymium, samarium, and dysprosium; the release of the group II elements was controlled by solubility of the sheet silicate formed in the surface layers. Group III contained silicon, aluminum, calcium, strontium, barium, magnesium, and chromium; the release of the group III elements was controlled by diffusion and decomposition processes in the glass, and was also affected by formation of the sheet silicate.