Abstract: The invention relates to a continuously advancing machine for works on a railway track, comprising a main chassis mounted on bogies and provided with a mobile auxiliary chassis supporting working members such as ballast tamping and track lifting/shifting units. The auxiliary chassis may move along the main chassis under the action of a bar for attachment to a chain driven by a motor and borne by a carriage, so as to advance, during the works, step by step with respect to the track while the machine progresses continuously. The reactions of inertia are entirely taken up by the track, via the carriage immobilized thereon thanks to grippers during the phases of advance of the auxiliary chassis and its working units.