A ferromagnetic material can be formed in a very small size on the order of an atomic size and is capable of being stably magnetized. The ferromagnetic material comprises basic unit structures each consisting of a first atom (11), a second atom (12) of the same kind as the first atom (11), and a third atom (or atomic group) (13) of the same kind as the first atom (11) or of a kind different from that of the first atom (11). In each of the basic unit structures, the atoms are arranged on a surface of a substrate so that a chemical bond (14) is formed between the first atom or molecule and the third atom or molecule, a chemical bond (14) is formed between the second atom or molecule and the third atom or molecule, and a chemical bond or an electron path (15) not passing the third atom is formed between the first and the second atom or molecule, wherein said third atoms or molecules consist of As atoms.