A new superconducting magnet system for bacterial cultivation was developed. The superconducting magnet has a horizontal room-temperature bore with a diameter of 160mm, and provides a homogeneous magnetic field of 7T±0.5% for a 200-mm-long by 100-mm-diameter region. This homogeneous field region contains an incubator, where bacteria are cultivated aerobically at 10 to 70°C±0.1°C while being shaken. The culture exposed to the high magnetic field is compared with a control culture incubated at below geomagnetic field strength. Cultivation of Escherichia coli was carried out both in homogeneous and in inhomogeneous fields, and 1.4-3.6 times the number of viable cells of the control culture was observed in a stationary phase.