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