A light detection module 1 that detects an interference beam LC that has exited from an exit end surface FS of an optical fiber F in an OCT device 100, the light detection module 1 being provided with: a ball lens 7A having an entry surface 71 for entry of the interference beam LC that has exited from the exit end surface FS, and an exit surface 72 for exit of the interference beam LC that has entered the entry surface 71; and a photodiode 8 having a detection surface 81 for entry of the interference beam LC that has exited from the exit surface 72; wherein the interference beam LC enters the entry surface 71 at an incline with respect to the normal 75 at an entry position 74 of the interference beam LC, the interference beam LC exits the exit surface 72 at an incline with respect to the normal 77 at an exit position 76 of the interference beam LC, and the interference beam enters the detection surface 81 at an incline with respect to the normal 83 at an entry position 82 of the interference beam LC.