The beneficial effects of chronic/repeated magnetic stimulation on humans have been examined in previous studies. Although pain relief effects have been reported several weeks after magnetic treatment, no report is available regarding the prompt effect of magnetic stimulations. In this study, a novel apparatus was developed to generate time-varying magnetic fields with rotating magnets. Adult, conscious rats were exposed to the rotating magnets in a posture in which their spines were parallel to the induced electric current. The magnetic field suppressed the paw withdrawal reflex in the anesthetized rats, and the suppression effect disappeared 5 minutes after magnets stopped rotating. The tail flick (TF) latency and mechanic withdrawal thresholds (MWT) of the rats were significantly increased by the rotating magnets; the increases positively correlated with the velocity and period of the magnet rotating. These analgesia effects recovered to the baseline level 30 minutes after magnets stopped rotating. A biophysics model was proposed to qualitatively understand the mechanism of pain inhibition by the rotating field. The prompt analgesia effect of the rotating magnets and its rapid recovery encourage the application of this technique as a promising new analgesia and anesthesia method.