Disclosed is a tape cassette including a cassette shell in which tape reels around which a tape-like recording medium is wound are contained; a mouth portion provided in a front portion of the cassette shell in such a manner as to be opened forwardly, upwardly, and downwardly, the mouth portion being positioned such that part of the tape-like recording medium crosses the front end of the mouth portion; and a front lid, provided on the cassette shell, for covering the front side of the tape-like recording medium; wherein both side portions of the mouth portion of the cassette shell are taken as tape extraction portions opened forwardly; and each of the inner surfaces of outer side surface front portions of the cassette shell, which forms each of the inner surfaces of outer side walls of the tape extraction portions, is formed into a taper surface which becomes wider outwardly as nearing the front end. With this configuration, it is possible to increase the degree of freedom in design of tape extraction guides of a tape drive apparatus, and to loosen the arrangement accuracy of the tape extraction guides.