To provide a liquid filling method and a device capable of preventing a bag mouth part from being deformed in the closing direction, and capable of preventing liquid filled in a bag from sticking to a seal expected part of the bag.

The liquid filling device comprises a liquid filling nozzle 22 having a downward discharge port 27 on the lower end and a gas jetting nozzle 31 having a gas jetting port 41 opening toward the side in the horizontal direction. The liquid filling nozzle and the gas jetting nozzle are lowered, the discharge port and the gas jetting port are put in a bag H, spraying on the seal expected part of the bag of pressurized gas is started simultaneously when starting filling of liquid or before it, and jetting of the pressurized gas is stopped simultaneously when stopping the filling of the liquid or by delaying from it.