In order to provide a recording tape cassette in which a recording tape can run
stably even if a non-recording surface side of the recording tape warps, there
is provided a recording tape cassette including a guide shaft, around which the
recording tape is wound such that the non-recording surface side thereof contacts
the guide shaft, for feeding the recording tape to an outside of the recording
tape cassette. outside diameter of the guide shaft becames larger the closer it
is to a central portion of the guide shaft in an axial direction.
