We developed a microscopic electro-optic field probe by directly depositing a lead zirconate-titanate [PbZr0.3Ti0.7O3] film onto optical fiber edge using aerosol deposition. Its fabrication process is virtually self-aligning because there are no complicated procedures such as fine lithography and etching. The lateral size of the film pattern is 125 μm, which is the same as the diameter of a typical single mode fiber, and the thickness is approximately 5 μm. An RF electro-optic signal was successfully measured over a microstrip line. The measurable bandwidth of the probe was over 2 GHz. Because it is very tiny and thin, the developed electro-optic probe has great potential for detailed electrical characterization in the microscopic regions of high performance electronic products such as the interconnecting parts between LSI packages and printed circuit boards and spaces among different LSI chips in a package.