A tape cassette (30) is provided with a box-shaped cassette case (31), a tape that is contained in the cassette case (31), a pair of cavities (64) that are provided at opposite ends of a diagonal line that connects one corner portion (322) to another corner portion (324), and a side face indicator portion (800) that indicates a type of the tape. The side face indicator portion (800) includes a plurality of indicator portions that are disposed in a pattern that is in accordance with the type of the tape. Each of the plurality of indicator portions is one of a switch hole (801) and a surface portion (802).