A computer mouse include a base; a cover assembly releasably secured to the base and including an opening; and a rotational device disposed in the opening to rotatably secure to the base. The rotational device includes a disc-shaped external rotational member including a circular flange on one surface, the circular flange disposed through the opening to rotatably secure to the base, the circular flange having a through hole; and a disc-shaped internal rotational member partially disposed in the through hole.