It has been reported that magnetic stimulation effectively eliminates urinary incontinence. However, this type of therapy has not been established as a practical treatment for urinary incontinence because of its poor power conversion efficiency and the leakage of current to regions other than that of the target of stimulation. It is therefore necessary to develop magnetic stimulators that are more efficient in stimulating the sphincter muscles and the peripheral nerves, and are more convenient than those presently available. By using a large-diameter coil, the magnetic stimulation method offers a larger current distribution over a wider area of the target region than electrical stimulation method, and the placement of the coil can be relatively easily changed to obtain better therapeutic results. We attempted, with a computer simulation model of the female abdomen, to simulate the distribution of the induced current density on the basis of biological tissue conductivity. We determined which method of stimulation is the most efficient by varying the stimulator coil location and size. A genetic algorithm (GA) was used for optimization.