To provide a cap with a nipple which prevents leakage of milk or a beverage in a container when a user carries the container and is attached to a plastic bottle or the like easily.

The cap with the nipple comprises a main body 1 of the cap attachable to and detachable from a mouth part 2a of the container 2, a nipple supporting member 3 attached to the main body 1, the nipple 4 having a base part 4a attached to the member 3 and made of a flexible body, and a cover 7 which is attached pivotally to the member 3 to open and close and prevents leakage of a liquid in the container 2 by bending the front end of the nipple 4 forcibly when closed to cover the nipple 4. Since milk or a beverage in the container 2 hardly leaks from the nipple 4 even if the user knocks down the container 2 by mistake or goes out with it, he/she is free from worries to mess the clothes or the like. Since the cap is attached to a plastic bottle easily, a beverage in the plastic bottle is given to a baby without transfer the beverage in the plastic bottle into a baby bottle.