A wireless mouse includes a base having a top surface defining a button region and a non-button region, and a top cover including a cover body that separably covers the top surface of the base. The cover body has an inner surface facing the non-button region of the top surface and an integrally formed groove defining member extending from the inner surface into a space disposed between the cover body and the top surface of the base. The groove defining member cooperates with the inner surface of the cover body to define a positioning groove that is open to the space between the cover body and the top surface of the base into which a wireless receiver is received and releasably retained.