Disclosed is a strength-enhancing apparatus for a metal part comprising a recovery mechanism for sucking powder flow dust generated from glass beads crushed on a surface of a gear in a chamber to recover it together with drainage, wherein the recovery mechanism includes a liquid-spouting means arranged on a ceiling in the chamber, for effecting showering for the whole interior of the chamber. Accordingly, it is possible to reliably recover the mist containing the powder flow dust floating in the chamber, and it is possible to reliably avoid adhesion and accumulation of the powder flow dust.