Abstract: A magnetic annealing device for inserting a recording medium 1 provided with an axial hole formed at a center thereof and having a disk shape into a chamber 10 and applying a heat treatment to the recording medium 1 in a magnetic field is provided with a magnetic circuit for forming a magnetic field in the chamber 10, the magnetic circuit comprises a pair of magnets 4 and 5 disposed with a distance therebetween along an axial direction of the axial hole and having magnetic fields directionally opposed to each other and a first ferromagnetic substance 6 disposed between the pair of magnets 4 and 5, wherein the recording medium 1 to be heat-treated is disposed at an intermediate position between the pair of magnets 4 and 5 facing each other in the state in which the first ferromagnetic substance 6 is inserted into the axial hole. A second ferromagnetic substance 7 having a ring shape is preferably disposed in a periphery of the recording medium 1.