The invention discloses an automatic magnetic field mutagenesis machine. A GM refrigerator is installed in a refrigerator cold box, a sample table is arranged in a magnet Dewar, an ultraviolet lamp is mounted on the sample table, an electric heating wire and a thermometer are also disposed below the sample table, a connecting rod is fixed on the sample table, the end of the connecting rod is connected to a motor, the magnet Dewar is also internally provided with a superconducting coil, the outside of the superconducting coil is equipped with an electric insulating layer, a liquid helium container, a 40K cold shield and a super thermal insulation layer in order, vacuum is kept between the liquid helium container and the40K cold shield and between the super thermal insulation layer and the Dewar inner wall, the first stage cold head of the GM refrigerator is in connection with the 40K cold shield, and the second stage cold head of the GM refrigerator is in connection with the liquid helium container through a helium and electrical transmission pipeline. The automatic magnetic field mutagenesis breeding machine provided by the invention can realize magnetic field mutagenesis under static and dynamic conditions so as to improve the strain output. With the advantages of novel structure and simple operation, the automatic magnetic field mutagenesis machine has very high application value.