A wireless computer mouse, comprising a mouse main body and a cover, said main body having a base housing, a top housing and a push-button case, said mouse characterized in that said cover has shape similar to that of said top housing, and has a hook on rear side thereof and at least one positioning plate on front side thereof, said top housing has a battery chamber therein, at least one positioning hole on the side wall of said battery chamber, locking hole on rear side of said chamber, when said cover is covered on said top housing and pushed forward, said hook is locked with said locking hole and said positioning plates are engaged into said positioning holes.