In this paper, we demonstrate a self-powered AC-current sensor using a piezoelectric connected-in-series approach to increase the sensitivity. The sensor consists of a CuBe-beam, piezoelectric-PZT-sheet, NdFeB hard-magnet, and mechanical-frame. When the sensor is placed in an alternative magnetic-field induced by an alternative current-carrying wire, the magnet fixed on the beam is subjected to an alternative magnetic-force produced by the magnetic-field. Therefore, the beam is oscillated. Consequently, the piezoelectric-sheet fixed on the beam is periodically deformed and continuously produces voltage-response. When beams are connected in-series, the total voltage-response is significantly enlarged while the background-noise remains the same. The experimental result shows the sensitivity of the sensor consisting 8 beams connected in-series under the magnetic-field generated by a wire of 8-Ampere from a breaker is enlarged from 130 mV/A to 640 mV/A.