PURPOSE: To obtain ferromagnetic metallic powder having an exactly needlelike shape and a large specific surface area by treating needlelike iron oxyhydroxide with a silicon compound, converting it into iron oxide, and sticking a silicon compound to the iron oxide to prevent sintering.

CONSTITUTION: Needlelike iron oxyhydroxide or needlelike oxyhydroxide of iron-base metal is treated with a silicon compound and dehydrated by heating at 300W800°C in a nonreducing atmosphere to form iron oxide particles or particles of oxide of said iron-base metal. The oxide particles are treated with a silicon compound and reduced under heating in a reducing atmosphere. Thus, sintering is prevented, and ferromagnetic metallic powder having a large specific surface area is obtd. while retaining the needlelike shape of the oxide particles.