To easily and securely analyze an electromagnetic field generated in large-scale facilities.

The electromagnetic field in an analysis region 21 can be analyzed without division into a multitude of elements, by calculating a mean magnetic flux density Bave generated at the central part 20e1 of the cross-section of a magnetic body 20e and at the equivalent element 31 occupied by the air at the sides thereof, the mean magnetic field Have, and the angle θBH between the mean magnetic flux density Bave and the mean magnetic field Have, by preparing, with the parameter of an angle θB, B-H curves 90-93 expressing the relationship between the calculated mean magnetic flux density Bave and the mean magnetic field Have and B-θ curves 100-103 expressing the relationship between the mean magnetic flux density Bave and the angle θBH, and by obtaining the magnetic flux line generated in the analysis region 21 using the prepared B-H curves and the B-θ curves. Accordingly, the storage capacity required for analyzing the electromagnetic field can be extremely reduced.