A winding device for a Venetian blind includes at least one support seat secured to a headrail to correspond to the position of at least one pull cord and having an inside formed with a through hole and a side formed with a guide hole, and at least one slide bushing mounted on a drive shaft to rotate therewith and pivotally mounted in the through hole of the at least one support seat. Thus, the wound pull cord pushes the slide bushing to move relative to the support seat during rotation of the slide bushing, so that the pull cord is wound around the slide bushing smoothly by movement of the slide bushing so as to lift the pull cord smoothly.
