An opening device for straws for liquid food containers enables a straw hole to be easily opened by piercing with a straw while avoiding easy leakage or breakage due to external force from vibrations or the like during delivery. The device includes a base and a main body, formed from packaging material, both sides of the base paper of which have been laminated with thermoplastic resin and a top, formed from thermoplastic resin, which is joined to the top of the main body. An opening of the opening device for straws, integrated with the top section, is provided with a plurality of step sections and between-step sections on the front and back surfaces. The front between-step sections and the back between-step sections overlap at the edge of each of the step sections, with the thickness at the edge of the between-step sections being thinner than that of the steps.