A synthetic resin container lid (2) has a shape including a body (4), which is mounted on a mouth-neck portion (56) of a container by locking a locking means (26) to a locked means (58) of the mouth-neck portion (56), and an upper lid (6) coupled to the body (4) via a hinge means (32). The synthetic resin container lid (2) is improved so that the entire container lid (2) is fully and easily detached from the mouth-neck portion of the container.