1. A magnetic field analysis method for analyzing a magnetic state of a permanent magnet obtained by magnetizing a magnetic material with a magnetizer, comprising: preparing a demagnetization curve by actual measurement of each incomplete magnetization region of a test permanent magnet, wherein the test permanent magnet was obtained by application of a magnetizing magnetic field to a magnetic material; calculating, with the use of said demagnetization curve, a region parameter related to an incomplete magnetization region of a permanent magnet to be analyzed, wherein the permanent magnet is the test permanent magnet, or is made of the same type of magnetic material as the test permanent magnet; and analyzing a magnetic state of the permanent magnet with the use of the calculated region parameter, wherein the incomplete magnetization region of the permanent magnet represents a region which cannot be magnetized until the permanent magnet is saturated.