To provide a substrate material for an internal wall, and a cleaning agent which each are obtained by a producing method consisting of admixing clay with water or hot water, and admixing therewith an oxide of aluminum and silicon, an alkali earth metal, and an alkali metal, followed by boiling the resultant admixture, or alternatively further adding thereto an inorganic material containing carbon.

There is provided an interior finishing material formed of an environment-friendly natural material, which can be easily applied to a room having a clay wall or a sand wall, is excellent in burning resistance and hygroscopic and dehumidifying properties, and dissolves in the soil when discarded. There is also provided an environment-friendly cleaning agent formed of an inorganic and natural material. The invention further provides a substrate material for an internal wall and a cleaning agent which each are obtained by a producing method consisting of admixing clay with water or hot water, and admixing therewith an oxide of aluminum and silicon, an alkali earth metal, and an alkali metal, followed by boiling the resultant admixture, or alternatively further adding an inorganic material containing carbon.