A position adjusting device includes a base unit with spaced-apart first and second lateral plates. A bracket is elongated and interposed between the first and second lateral plates for mounting an integration rod, and includes opposite first and second open ends. A connecting mechanism includes two resilient pins connected respectively between the bracket and the first lateral plate and between the bracket and the second lateral plate. The resilient pins are proximate to the first open end of the bracket. An adjusting member extends through the first lateral plate, and abuts against one side of the bracket proximate to the second open end. The adjusting member drives the bracket to move along a first axis and a second axis perpendicular to the first axis. The first and second axes are perpendicular to an extension direction of the bracket.