To provide a stroboscopic unit assembling jig, with which stroboscopic units produced in a large quantity are efficiently assembled and inspected.

In the stroboscopic unit assembling jig to assemble the stroboscopic unit provided with a printed circuit board, on which at least a photodetector is packaged, photodetector-positioning part to position the photodetector in the direction which is in parallel with the plate face of the printed circuit board on the printed circuit board, and an elastic part to bring the rear end part of the photodetector into close-contact with the plate surface of the printed circuit board by pressing the top end part of the photodetector and a printed circuit board positioning part to position the printed circuit board in the direction in parallel with and a direction perpendicular to the plate face are provided.