The present invention discloses a locating structure for slide rail, comprising a guide rail which is a rectangular plate disposed with a respective inward-turn slide groove on both sides of its bottom plate, wherein at least two locating holes at the predetermined locating positions are machined to form on the surface of the bottom plate; a slider which is a short frame whose slide plate on top extends to form a respective slide wing on its both sides corresponding to the slide grooves to form a socketingly connection, wherein a respective receiving hole is manufactured to form on both sides of the slide plate, a spring frame, disposed on the bottom of the slide plate and manufactured to form a ball hole on its bottom to socketingly connected with a rolling ball, extends upward an predetermined length from its both sides, respectively, and then bends inward to form a turn portion, respectively, one of which connects downward with a spring plate whose bottom contacts with the rolling ball and the other of which maintains a gap with the spring plate; when the slider slides, the two slide wings slide along the two slide grooves, respectively, and thus the rolling ball compresses the spring plate and moves along the bottom plate until the rolling ball reaches the locating hole to stretch the spring plate, such that the rolling ball falls into the locating hole to form a snapping engagement.