PROBLEM TO BE SOLVED: To provide a magnetic field generator capable of heightening uniformity of the magnetic field, and suppressing enlargement of the whole device.SOLUTION: A current variable correction coil 4 for generating a magnetic field for correcting uniformity of a magnetic field generated by a main coil 2 formed by winding ReBCO-based superconducting wire is provided inside the main coil 2. The magnetic field generated by the current variable correction coil 4 is hardly affected by a shield current flowing in a superconducting layer of the ReBCO-based superconducting wire.【課題】磁場の均一度を高め、且つ、装置全体が大型化するのを抑制することが可能な磁場発生装置を提供する。【解決手段】ReBCO系超電導線材が巻回されてなるメインコイル2が発生させる磁場の均一度を補正する磁場を発生させる電流可変補正コイル4を、メインコイル2の内側に設ける。電流可変補正コイル4が発生させる磁場は、ReBCO系超電導線材の超電導層に流れる遮蔽電流の影響をほとんど受けない。【選択図】図1