A tape cassette comprises an upper half casing and a lower half casing and male hollow cylindrical projections having a notch mounted on either of the upper half casing or the lower half casing and female hollow recesses mounted on the other half casing at the corresponding positions. The upper and lower half casings are superposed to fit the male hollow cylindrical projects into the corresponding female hollow recesses and are fixed together by screwing self-tap bolts from the female hollow recesses into the male hollow cylindrical projections having notches to fix the projections on the inner surfaces of the female hollow recesses.