A tape cassette includes a cassette case, a tape roll housed in the cassette case, an arm portion that guides a tape, and a long hole extending in a left-right direction of the cassette case and formed straddling a center position of the cassette case in the left-right direction, wherein a first distance (a length of the tong hole in the left-right direction) is larger than a second distance (a length from an end portion of the tape cassette in an opposite direction to a feed direction of the tape fed in the arm portion, to an end portion of the long hole in the opposite direction), and a center of gravity of the tape cassette is located in a specific area whose both end positions in the left-right direction are the same as those of the long hole, and which extends in a front-rear direction.