The object of the invention is to provide a biomagnetism measuring device using a high-performance cylindrical shielding apparatus provided with a flange-type plate having an opening formed on a circumferential face, an auxiliary cylinder in which one or plural cylindrical members are connected so that the central axis of the opening of the flange-type plate and each central axis of the cylindrical members are coincident, cylindrical shields having first, second and third angular ranges with the y-axis, a revolving door having a cutout in a portion parallel to the y-axis and acquired by integrating the cylindrical shields, shield bases for supporting the cylindrical shield to which the flange-type plate is connected in a circular-arc part at both ends, revolving parts for revolving the revolving door in a circumferential direction of the y-axis along a circumferential part of the cylindrical shield and opening or closing an opening in the circumferential direction, a cryostat arranged inside the opening of the auxiliary cylinder and the opening and a SQUID fluxmeter arranged on a measurement face parallel to an XY plane inside the cryostat held at low temperature and characterized in that the circumferential part of the cylindrical shield is inserted between the circumferential parts of the cylindrical shields when the revolving door is closed, cylindrical internal space is formed and an environmental magnetic field that invades the internal space is screened.