A liquid-containing container manufacturing method includes: a liquid blow molding step of, in a state in which a reversal panel formation part forms a convex surface projecting toward inside of a cavity, supplying a pressurized liquid into a preform placed inside a cavity, to mold the preform into a container including a reversal panel; and a headspace formation step of pressing the container by a press part to reverse the reversal panel, and thereafter releasing press by the press part to increase a volume of the container and thereby form a headspace.