A magnetic tape cassette includes a case that is formed by joining an upper half and a lower half, one or more tape reels, a window and a reel urging member having a tape reel contacting portion which contacts an upper part of the tape reel(s), bent arms connected to opposite sides of the tape reel contacting portion and sliding end portions provided at distal ends of the bent arm. A slide groove is provided in an inner surface of a perimeter of a window opening in the upper half and a window member has hold-and-retain portions which hold the sliding end portions in cooperation with a bottom surface of the slide groove into which the sliding end portions have been fitted. A tape reel suitable for use with the magnetic tape cassette, a resinous leaf spring and its production process are also provided. Tape reels housed in a cassette case can be urged toward the lower half by a member whose structure is simple and permits easy fitting and removal. Assorted collection of constituent materials, particularly for assorted collection of resin materials and selective collection of resin materials as separate from metal materials are possible.