An apparatus and method for inspecting a circuit of a substrate is described. The apparatus includes a pin probe coming into contact with a first end of an electrode formed on a first side of a substrate, a voltage source for applying a voltage to the pin probe, a film disposed at a second end of the electrode formed on a second side of the substrate, a dielectric fluid sealed in the film, and an electronic ink dispersed in the dielectric fluid, and charged with electricity to flow when the electrode is electrified. The present invention is advantageous in that whether an electrode has been electrified is measured using charged electronic ink, so that the use of a pin probe is limited to one side of a substrate, thus reducing cost required for the entire inspection.