A method of preparing a simple ceramic ingot of a spent filter having radioactive cesium trapped therein, and a ceramic ingot of a spent filter having improved properties such as leach resistance, thermal stability, and cesium content are provided. The method includes grinding and mixing a spent filter having cesium trapped therein, adding a solidifying agent, and sintering the spent filter. The method of preparing a ceramic ingot of a spent filter can be useful in preparing the ceramic ingot of the spent filter from only the spent filter by means of simple grinding and sintering, and in preparing the ceramic ingot of the spent filter by adding a small amount of a solidifying agent. The ceramic ingot of the spent filter has a high density and improved thermal stability, and shows improved leach resistance since a leach rate of a radioactive material is remarkably low. Therefore, the spent filter having radioactive cesium trapped therein can be effectively used to prepare a stable ceramic ingot.