<p>The magnetic tape cassette according to the present invention comprises a cassette case which is formed by assembling an upper and a lower cassette halves, and a pair of tape reels (1) around which a magnetic tape (47) is wound rotatably held in the cassette case. The lower cassette half is integrally formed with tape guides (114) for guiding the magnetic tape (47). Each of the tape guides (114) has a cylindrical part which includes in its circumferential direction a curved portion with which the magnetic tape (47) slidably contacts. The curved portion has a thickness larger than those of other circumferential portions of the cylindrical part. <IMAGE></p>
