a cap includes a cap body attached to a discharge port portion of a container and having a pouring port through which a content of the container can be discharged , and a lid pivotally supported by the cap body and capable of opening and closing the pouring port . the cap is provided with : a pushing member whose intermediate portion is pivotally supported by a pivotally supporting portion on a side surface of the cap body , the pushing member being swingable about the pivotally supporting portion ; and a thin - walled hinge for connecting an end portion of the pushing member and a rotatably supporting portion of the lid , the thin - walled hinge being adapted to convert swinging motion of the pushing member into motion for opening or closing the lid as an upper portion or a lower portion of the pushing member is operated by being pushed .