The growth of undesired bacteria causes numerous problems. Here, we show that locally enhanced electric field treatment (LEEFT) can cause rapid bacteria inactivation by electroporation. The bacteria inactivation is studied in situ at the single-cell level on a lab-on-a-chip that has nanowedge-decorated electrodes. Rapid bacteria inactivation occurs at the nanowedge tips where the electric field is enhanced due to the lightning-rod effect. Electroporation induced by the locally enhanced electric field is the predominant mechanism. The antimicrobial performance depends on the strength of the enhanced electric field instead of the applied voltage, and no generation of reactive oxygen species (ROS) is detected when >90% bacteria inactivation is achieved. Quick membrane pore closure under lower voltages confirms that electroporation is induced in LEEFT. This work is the first-time visualization and mechanism elucidation of LEEFT for bacteria inactivation at the single-cell level, and the findings will provide strong support for its future applications.