PURPOSE: Soft magnetic alloy for dental surgery, obtained by alloying Co, Cu, Au at a specific ratio, using combined with rare earth Co base permanent magnet having a high magnetic energy.

CONSTITUTION: Alloy, composed of Co;15W65%, Cu;5W50%, Au;30W80% and one or more than two kinds of Mn, Zn, Sn, Al, Si, Mg as deoxidizer for obtaining casting alloy having no blow hole at not more than 5%. The soft magnetic alloy 3 having the above mentioned compostion, is filled in the root part of the tooth 2 remained in the flesh part 1. The rare earth Co base magnet 5 haing a high magnetic energy, is put in the crown part of the tooth 4 so as to face the one hand magnetic pole against the alloy 3 and both are fixed by the magnetic sucking force. Thus, the above method is able to use for filling and reform of dental surgery effectively.