PURPOSE: To freely write a data on a label by the user by interposing the label between a main wall of the cassette and an openable window.

CONSTITUTION: A housing 9 composed of two main walls 11 and 13 and plural traverse walls is formed by the cassette 1 for housing the magnetic tape. The 2nd main wall 13 out of these main walls 11 and 13 has no holes. This main wall 13 is provided with the openable window 39 and two transparent windows 41 and 43, and the reels 6 and 8 and wound parts 5 and 7 are visible through these windows. Then, the label is interposed between the window 39 and the main wall 13, and the window 39 is fixed by engaging a tab 45 with a recessed part of the housing 9. In this constitution, when a data is written on the label 37, the window 39 is easily detached to do so.