A filling channel opening and closing device, which is used in a liquid product filling apparatus, including an opening and closing control unit that includes a flexible tube and a chamber enclosing the flexible tube in a gastight manner, a gas supply and exhaust device that collapses and restores the flexible tube by supplying pressurized gas into the chamber and exhausting the gas from the chamber, and a control device that controls the timing of supply and exhaust of the gas of the gas supply and exhaust device.