To provide a rotary table fixing structure for a travelling pile driver, ensuring the fixation of a pile driving hammer installed on a rotary table during pile driving by means of a simple composition.

The travelling pile driver is composed of the rotary table 3 mounted rotatably on the upper part of an automobile body, a moving guide part installed so as to be able to advance and retreat in a prescribed direction on the rotary table 3, and the pile driving hammer installed at the end of the moving guide part. A hydraulic cylinder fixing member 4 is installed on the peripheral edge of the rotary table 3. The end of the expansion part 1a of a hydraulic cylinder 1 is fixed to the fixing member 4, and the fixing part 1b of the hydraulic cylinder 1 is rotatably installed in the automobile body.