Abstract: Disclosed is a cap for a drink container which permits drinking of the drink contained therein without removing the cap. The cap comprises a cover plate which is to cover the upper opening of the drink container and a peripheral wall of the cover plate which is to be fitted to the upper opening edge of the drink container. The cover plate is disposed diagonally in the peripheral wall and has a liquid port at a low position. A plugging member for closing the liquid port is pivotally supported on the upper surface of the cover plate substantially at the center thereof. The peripheral wall has a notch in which the plugging member is to be retracted when the liquid port is closed thereby. The plugging member is locked onto the cover plate when the liquid port is closed by the plugging member, whereas the plugging member is locked onto the peripheral wall when the liquid port is let open.