To provide a slat elevating device for a horizontal blind, which facilitates switching of an elevating code drawing direction from a frontward direction to a rearward direction of a head box and vice versa, to thereby facilitate switching of an operating location of the elevating cord on a right side or a left side of the head box.

According to the structure of the horizontal blind, slats are elevated by pulling the elevating cord out of the head box while they are lowered by taking up the elevating cord into the head box, and the elevating cord is hung from the head box via a stopper device for preventing the slats from lowering due to their self-weight. The slat elevating device is comprised of engaging means 22a, 22b, 23a, 23b for supporting the stopper device in a manner movable frontward and rearward of the head box, and elastically engaging with the stopper device at a moving edge of the same, and a disengaging means 21a, 21b for disengaging the engagement of the engaging means.