Fibromyalgia is a disease of unknown origin in which sleep involvement is very prevalent, and one of the main symptoms, even as prevalent as pain. In fact, one condition has been linked to the other, and the two may feedback on each other. We investigated what happens if by applying low-field magnetic stimulation in patients with fibromyalgia, it could improve sleep variables, and if this would be related to an improvement in the pain of the patients. We compared the results of a group of female patients with fibromyalgia, who underwent treatment for 6 weeks, with another group of patients with similar characteristics, who were not treated. The results were also compared with a group of healthy women, who served as a second control group. The Pittsburgh sleep scale was used as a sleep scale and a global clinical scale was used to assess general state. A significant improvement was observed in the different items of the sleep scale applied, from the four weeks of treatment, being even more evident at the end of treatment at six weeks. A total of 82% of patients improved at the end of treatment. There was a correlation of this improvement with the overall pain situation of the patients. In addition, there was a trend towards equal sleep outcomes between treated patients and healthy subjects. Treatment with low intensity magnetic stimulation could improve the sleep of fibromyalgia patients, as well as their overall clinical situation, and both processes could be interrelated.