In the present invention, when measuring magnetism of a measuring portion of a patient by making use of a dewar incorporating magnetism sensors each including a super conducting quantum interference device, a bed is at first positioned outside a position immediately below the dewar. At this position outside the position immediately below the dewar the patient is laid on the bed in an inspection posture. Marks are attached on the body of the patient at three points for setting X and Y axis coordinate on the measurement portion, at the position outside the position immediately below the dewar cross shaped beam patterns are projected and the position of the bed is adjusted so that the marks at the three points locate on the cross shaped beam patterns, thereafter, bed is transferred by a constant amount to the position immediately below the dewar. Thereby, in the biomagnetism measurement the correlated position between the dewar (magnetism sensors) and the measurement portion of the patient can be ascertained easily and accurately.