In spark plasma sintering (SPS), it is supposed that a part of the large pulsed sintering current flows into the specimen and affects the sintering behavior. To clarify the influence of the internal pulsed current that flows through the specimen during SPS, measurement of the electrical resistance of the specimen was conducted using Pt electrodes and the internal pulsed current was successfully observed using a magnetic probe during the sintering of ZnO and other materials. Two Pt electrodes were installed on the sides of a ZnO sample through a carbon die, and decrease of electrical resistance was observed with the progress of sintering. The internal current that flows through the specimen during SPS was several hundred ampere, and the ratio of the internal current to the total current was found to be dependent on the material and the progress of SPS process.