We developed a microscopic electro-optic field probe by directly depositing a lead zirconate-titanate [PbZr_0.3Ti_0.7O₃] film onto the optical fiber edge using aerosol deposition. Its fabrication process is low-cost and relatively easy because there are no complicated procedures such as fine lithography and etching. The lateral size of the film is 125µm, which is the same as the diameter of a typical single mode fiber, and the thickness is approximately 5µm. An RF electro-optic signal was successfully measured over a microstrip line. The capability for detecting GHz range fields is also shown. 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.