A hanger device includes an open-back metal housing having two sidewalls formed with a notch each, and a hook connected to a bottom thereof; a plastic seat embedded in the metal housing and having a transverse recess; a release control element vertically slidably connected to the plastic seat; and at least one tension spring located between the release control element and the plastic seat. The notches have outward and downward inclined upper edges and a vertical sectional shape the same as the recess. The hanger device can be firmly attached to a horizontal rail with the inclined upper edges of the notches tightly hooked to a rearward and downward inclined upper end surface of the horizontal rail and a projected block on a top of the release control element upward pushed by the tension spring into an open-bottomed channel at a lower end surface of the horizontal rail.