A lens adjusting mechanism includes a fixed board, a movable board, two first sliding blocks, a first driving device and two second sliding blocks. The movable board is provided on the fixed board. The first sliding blocks, each of which has two first driving members connected to the first sliding blocks, are provided on the movable board for movement along an X axis. The first driving members drive the first sliding blocks moving along a Y axis together with the movable board. The second sliding blocks, each of which has two second driving members pivoted on the fixed board and connected to the second sliding blocks, are provided on the movable board for movement along the Y axis. The second driving members drive the second sliding blocks moving along the X axis together with the movable board.