To provide a backlight enhanced in the utilization efficiency of the light of a light source, a display device, and a reel type game machine.

The backlight 1 is constituted of the light source 10 comprising, e.g., a chip LED, a printed wiring board 14 on which the light source 10 is mounted and a holder 11 having a recessed section 12a with an inverted truncated pyramid shape and holding the printed wiring board 14 in the bottom of the recessed section 12a with exposing the light source 10. The inner face of the section 12a reflects the light of the light source 10. The light emitted from the light source 10 and incident to the inner face of the recess 12a is reflected to the inner face of a reel 2, and the the light reflected by the inner face of the reel 2 is reflected by the inner face of the recess 12a and again is incident to the reel 2, consequently the utilization efficiency of the light of the light source 10 is enhanced.