PURPOSE: To accomplish foaming of material by letting air supplied from a motor-driven air feed pump flow through an air feed pipe to an exhaust portion, so that the air is passed through a lot of air holes of the uniform size of the exhaust portion to be formed into air bubbles which are released into the mate rial.

CONSTITUTION: Air taken in from the outside by a motor-driven air feed pump 101 is passed through an air feed pipe 102 to an exhaust portion 103, and re leased as a lot of air bubbles through air holes of the exhaust portion 103. The size of the air hole of the exhaust portion 103 is arbitrary, and it is possible to change to the air hole of a different size of the exhaust por tion 103. It is desirable that the air feed amount of an air feed pump 10 can be controlled. If there is a little material to be foamed by air bubbles released from an exhaust portion of a very thin plate-like form, which is placed at the bottom of a receptacle where material is put, or even if foaming proceeds and there is a little material not yet foamed, the material can be foamed effectively. Furthermore, the generated foams are of the uniform size, so that a cook can be made with very high quality.