A high-frequency magnetic field generating device includes two coils arranged with a predetermined gap in parallel with each other, the two coils (a) in between which electron spin resonance material is arranged or (b) arranged at one side from electron spin resonance material; a high-frequency power supply that generates microwave current that flows in the two coils; and a transmission line part connected to the two coils, that sets a current distribution so as to locate the two coils at positions other than a node of a stationary wave.