PURPOSE: To obtain a homogeneous and integral inorganic foamed body by using a nonfoamed raw material having nearly same composition as the foamed body and joining inorganic foamed bodies with each other and foaming the joined parts.

CONSTITUTION: Inorganic foamed bodies consisting of natural vitreous mineral such as SHIRASU (volcanic glass) and obsidian as a main component are joined with each other by using a nonfoamed raw material having nearly same composition as these foamed bodies. Then these inorganic foamed bodies are integrated with each other by foaming these joined parts. In the above-mentioned foaming and joining method, since the nonfoamed raw material is infiltrated into the pores of the porous inorganic foamed bodies and foaming is performed in these pores, the inorganic foamed bodies can be tightly joined to the joined parts. Furthermore physical properties such as thermal expansion coefficient are made same because the composition of the joined parts is same as the inorganic foamed material. Therefore stress is not acted on the joined parts by the change of environment such as change in temp. and the generation of crack is not caused thereby.