The present invention addresses the problem that the injection amount of a liquid electrolyte (26) becomes excessive because the liquid electrolyte (26) is volatilized at the time of injection if the liquid electrolyte (26) remains in a chamber (14). A device for injecting the liquid electrolyte into a battery has a liquid injecting pump (17) for injecting the liquid electrolyte into the battery (1) positioned inside the chamber (14) which has been sealed in a depressurized state and a vacuum pump (16) for depressurizing the inside of the chamber (14). A vacuum attainment time until a pressure of the inside of the chamber (14) becomes in a predetermined vacuum state is measured, and if this vacuum attainment time becomes longer than a predetermined value, the injection amount of the liquid electrolyte is corrected downwards.