An attachable cup includes a container and an attachable device for a toothbrush, and the attachable device includes at least one part of the container. An attachable device is for attaching a container to a toothbrush. The attachable device uses a fastening method, a gripping method, a clamping method, a locking method or the like to attach the attachable cup to a toothbrush. Once the attachable device attaches the attachable cup to a toothbrush, the operator can use the attachable cup for oral rinsing.