To prevent dust and the sweat of a hand from being stuck to a mouse pad by freely attachably and detachably attaching the cover having a size for covering the top of a mouse with excess to the mouse and using the mouse with the cover on.

Since this cover 2 is formed in the size for covering the mouse 1 from the top and leaving the excess, when the excessive width is adjusted to the size for mounting the entire palm, when the mouse 1 is held with the hand from the top of the cover 2, a part of the palm is prevented from directly touching the mouse pad. Further, since a part of the palm functions so as to press the cover 2 on the mouse pad, in the case that the cover is made of cloth, the mouse pad is cleaned by the cover 2 at all times. Since the cover 2 is fixed to the mouse 1 by a hook-and-loop fastener 3 and the hook-and-loop fastener 4, the cover 2 is not detached at the time of using the mouse. Then, the cover 2 can be washed anytime by making it attachable and detachable to/from the mouse 1.