Provided is a tunable magnetic field amplifying device capable of easily adjusting resonance frequencies and tuning usable bands by using discrete elements to vary electric properties of elements that are used for amplifying a magnetic field of a specific microwave band. The tunable magnetic field amplifying device includes a Swiss roll formed by winding a metal sheet coated with a dielectric in a spiral cylinder shape once or several times; and a tunable capacitor connected between an inner sheet of and an outer sheet of the metal sheet for tuning a resonance frequency.