PURPOSE: To make a lid-opening motion easier when a tape cassette in a case is taken out, and also make a lid opening motion in the production assembly line more assured and easier by providing a recessed part at a location which is closer to a front surface plate on respective case external side surfaces of a pair of side surface plates.

CONSTITUTION: When the lid of a case C is opened, while supporting a storage main body part 1, recessed parts 9 of side surface plates 8, 8 are pinched by fingers, and the lid is lifted upward. At that time, the fingers are put on the upper end edges of the recessed parts 9, and the lid is assuredly and easily lifted as the fingers do not slip, and the lid can be opened. Also, by providing the recessed part 9 at locations which are closer to front surface plates 7, 7 on the side surface plates 8, 8, the force is applied to a location which is away from a hinge part, and a moment force around the hinge can be effectively generated, and the lid can be opened by a smaller force. Also, in the production line of a tape cassette, when the lid is opened by a machine, a jig can hold the recessed parts 9, 9 on the side surface places 8, 8 in the same manner, and the jig is put on the upper end edges and does not slip, and the lid can be pushed up or pulled up.