A near-field scanning microwave microprobe (NSMM) technique has been used to investigate the magnetic properties of the Permalloy (Ni(81)Fe(19)) thin film. To characterize the hysteresis behavior of the magnetoresistance (MR) of Permalloy (Py) thin films, the microwave reflection coefficient, S(11) was measured. The change of the estimated MR was observed under in-plane external magnetic fields, and was confirmed with variation of MR measured by the 4-probe method. The magnetic properties of the Py thin film were examined by a vibrating sample magnetometer. The observed MR was correlated with the changes of the relative magnetic permeability. Delta mu of the Py. We also directly imaged the Py thin film changes by NSMM. MR of Py was determined from the visualized microwave reflection coefficient changes Delta S(11) at the thin film interface with high sensitivity. The present methodology can be extended to investigations of other magnetic thin films or magnetic materials using the NSMM system. (C) 2010 Elsevier B.V. All rights reserved.