A highly sensitive and broadband method of obtaining thin f lm permeability without sample-size limitations was developed based on the change in high-frequency impedance due to the skin effect. A microstrip probe with impedance matching of 50 Ω was fabricated, and placed in proximity to a magnetic thin film. The permeability was optimized with the Newton–Raphson method. The permeability of CoFeB f lm (45 mm 25 mm and 0.5 m in thickness) and that of FeCoB/Ru film (50 mm 40 mm and 0.2 m in thickness) were evaluated using a permeameter. The measured values were in rough agreement with theoretical values based on the Landau–Lifshitz–Gilbert equation and eddy current generation up to 30 GHz. The proposed method offers promise for measuring the permeability of wafer-sized samples in line because it is not restricted by size limitations.