A cassette accommodating case which can accommodate a plurality of cassettes but which has a generally thin structure and which can provide excellent storing convenience. The case includes a cover member having a pocket for receiving end portions of magnetic tape cassettes and a casing member having rotation stopper projections, with the cover member and the casing member being pivotably assembled. The pocket is formed so as to be large enough to receive the side end portions of the magnetic tape cassettes superposed in a reversed relation with respect to one another. A recess portion for receiving the thick portion of one of the superposed magnetic tape cassettes is formed on a wall surface of the cover member while a recess portion for receiving the thick portion of the other superposed magnetic tape cassette is formed on a wall surface of the casing member.