A microwave near-field sensing technique with sub-wavelength resolution is proposed for nondestructive local characterization of materials. The method is based on the measurement of a transmission coefficient by means of an association of a vector network analyzer, a hybrid coupler, an evanescent microwave coaxial probe, and an impedance tuner built up with a high precision programmable delay line and a variable motor-driven attenuator. Simplicity of operation and tuning possibility of the measurement sensitivity in the presence of the material under investigation are competitive advantages of the method. The depth and lateral resolutions of the microscope are experimentally verified.