PURPOSE: To prevent the limitation to the product uses by forming an ingot obtd. by sintering a mixture of the powder of thickened molten metal and a foaming agent in a nonfoaming state into a wire rod and foaming the same at the inside of a metallic pipe.

CONSTITUTION: Molten metal is added with a thickener and is imparted with sufficient viscosity, which is thereafter powdered. This powdered metal is uniformly mixed with a prescribed amt. of foaming agent, and this mixture is heated to the foaming starting temp. of the foaming agent or below and is sintered to obtain an ingot. This ingot is subjected to plastic working into a wire rod, and this wire rod is covered with a metallic pipe having an inside diameter higher than the diameter of the wire rod. This wire rod and metallic pipe are heated at the foaming starting temp. of the foaming agent or above to foam the wire rod, and the inside of the metallic pipe is filled with the foamed metallic material to obtain the foamed metal composite metallic wire.