A light measurement device 1 measures the intensity of laser light L output from a catheter tip end portion 31a of a catheter 31 having a built-in optical fiber 33. The light measurement device 1 includes a light receiving part 6 which receives the laser light L output from the catheter tip end portion 31a and a mounting part 7 which is disposed at a position facing the light receiving part 6. The mounting part 7 defines a position of a tubular hoop 36, which accommodates the catheter 31, with respect to the light receiving part 6. In a state in which the position of the hoop 36 is defined by the mounting part 7, the light measurement device 1 obtains the intensity of the laser light L by inputting the laser light L to the light receiving part 6.
