A cover for use with a portable information processing apparatus that comprises a main body housing formed with an attaching portion that includes a first surface and second surfaces adjacent to the first surface, a specific side of the housing including the first surface and an area adjacent to the first surface, the attaching portion being attached with the cover, comprising: oblong a first cover portion that covers the first surface; second cover portions that are formed at both ends of the first cover portion in a first direction, respectively, and cover the second surfaces; first fitting projections that are formed at two places on inner surfaces of the second cover portions, respectively, and fit into fitting recesses that are formed on the second surfaces; a hook that is formed on one end edge of the first cover portion in a second direction orthogonally intersecting the first direction to be projected from an inner surface of the first cover portion, and is inserted into a hook recess that is formed on the first surface to be extended from the first surface to a boundary between the first surface and the area adjacent to the first surface; characterized in that the attaching portion includes slide switches (22, 24) that are arranged on the second surfaces, and by first notches that are formed at a side of another end edge opposite to the one end edge that the hooks are formed in the second direction on the second cover portions, and for releasing fitting of the first fitting projections and the fitting recesses; and second notches that are formed on the second cover portions, respectively, and for securing movable ranges of operation knobs of the slide switches (22, 24), wherein the first notches are formed with intervals from the second notches, and one of the two first fitting projections is arranged within the intervals. oblong a first cover portion that covers the first surface; second cover portions that are formed at both ends of the first cover portion in a first direction, respectively, and cover the second surfaces; first fitting projections that are formed at two places on inner surfaces of the second cover portions, respectively, and fit into fitting recesses that are formed on the second surfaces; a hook that is formed on one end edge of the first cover portion in a second direction orthogonally intersecting the first direction to be projected from an inner surface of the first cover portion, and is inserted into a hook recess that is formed on the first surface to be extended from the first surface to a boundary between the first surface and the area adjacent to the first surface; the attaching portion includes slide switches (22, 24) that are arranged on the second surfaces, and by first notches that are formed at a side of another end edge opposite to the one end edge that the hooks are formed in the second direction on the second cover portions, and for releasing fitting of the first fitting projections and the fitting recesses; and second notches that are formed on the second cover portions, respectively, and for securing movable ranges of operation knobs of the slide switches (22, 24), wherein the first notches are formed with intervals from the second notches, and one of the two first fitting projections is arranged within the intervals.