A high-vacuum die-casting method includes an injecting step of moving a plunger in a sleeve so that a molten metal fed to the sleeve is pushed by the plunger to be injected into a cavity formed by a fixed mold and a movable mold, a cavity vacuumizing step of vacuum absorbing a gas in the cavity to discharge the vacuum-absorbed gas to the outside through a first path, and a sealed space vacuumizing step of vacuum absorbing a gas in a sealed space in which an eject plate and one ends of eject pins are arranged to discharge the vacuum-absorbed gas to the outside through a second path while the injecting step is performed. The sealed space vacuumizing step is started prior to the cavity vacuumizing step.