A mounting apparatus for fixing a slide rail to either a first rack post or a second rack post with different sizes or shapes of locating holes, includes a mounting bracket secured to the slide rail, a latch member rotatably mounted to the mounting bracket, and a restoring member. The mounting bracket includes a locating pin having a first segment adapted to extending through the first rack post locating hole, and a second segment adapted to extending through the second rack post locating hole. The latch member includes an arm received in the locating pin, with first and second holding teeth. In the locking position, either the first or the second teeth extend out of the locating pin to clasp the first or the second rack post, the unlocking position is achieved against spring pressure.