In the society with high environmental consciousness, development of new treatment techniques in used disposable diapers, which are currently mostly disposed by incineration, is needed. In this paper, a new treatment technique for decomposing disposable diapers by microorganisms with cryptomeria chips is proposed. In addition, a small size disposal system has ability to process steady like a garbage disposal unit is expected to develop. For that reason, the disposal process of disposable diapers is modeled, and the parameters of constructed process model are defined according to the results of experiment. Then a simulation with the parameters is performed used SIMULINK and MATLAB.