In JT-60SA fusion machine, the negative-ion-based neutral beam injector (N-NBI) is designed by Japan Atomic Energy Agency (JAEA) to inject 10 MW, 100 s D0 beams from two negative ion sources, each of which produces 22 A, 500 keV D− ion beams. In order to produce such high-power D− ion beams for 100 s, a large negative ion source with multi-aperture grids has been developed by modifying the JT-60U negative ion source. This paper reports the experimental results of the relation between LEF and voltage holding capability of JT-60 negative ion source by changing the number of apertures.