The magnetic field by the eddy current which occurs due to the impression of the inclined magnetic field, not only impression direction of the inclined magnetic field concerning the direction which differs from the impression direction of the inclined magnetic field it designates that it revises as purpose. In order to achieve this purpose, this invention seeks the compensating magnetic field which compensates the eddy current magnetic field which in the direction which differs from the impression direction and the said impression direction of the test inclined magnetic field making use of the test inclined magnetic field, occurs respectively to every direction respectively, the case of occurrence of the optional inclined magnetic field, generates the compensating magnetic field which compensates the eddy current magnetic field which accompanies the impression of the optional inclined magnetic field with the said optional inclined magnetic field, on the basis of the eddy current magnetic field of each direction which is measured to every direction respectively.傾斜磁場の印加により発生する渦電流による磁場を、傾斜磁場の印加方向のみならず傾斜磁場の印加方向と異なる方向についても補正することを目的とする。この目的を達成するために、本発明は、テスト傾斜磁場を用いて、テスト傾斜磁場の印加方向と該印加方向と異なる方向とにそれぞれ発生する渦電流磁場を方向毎に補償する補償磁場をそれぞれ求め、任意の傾斜磁場の発生の際には、該任意の傾斜磁場と共に、計測された各方向の渦電流磁場に基づいて任意の傾斜磁場の印加に伴う渦電流磁場を方向毎に補償する補償磁場をそれぞれ発生する。
