An optical-electrical converting device includes a printed circuit board (PCB), a light emitting module, a light receiving module, an optical coupling lens, and a locating frame positioned on the PCB. The PCB has two first locating elements. The optical coupling lens includes a first converging lens and a second converging lens. The locating element has two second locating elements. The two first locating elements and the two second locating elements cooperate to position the locating frame on the PCB. The locating element further has two third locating elements. The optical coupling lens has two fourth locating elements. The two third locating elements and the two fourth locating elements cooperate to position the coupling lens on the locating frame, and thus the first converging lens is aligned with the light emitting module, and the second converging lens is aligned with the light receiving module.