PURPOSE: To ensure smooth slide operation by arranging the slide operation cylinder of a track frame immediately below a rotary joint in the construction wherein the track frame is so mounted as to be slidable in a crosswise direction at both sides of a pair of front and rear support guides on a travel machine bed.

CONSTITUTION: Tube shaped support guide parts 8a and 8b are formed at the front and rear positions of a turntable turning axis line X of a crawler type travel machine table 2, and each track frame 10 of right ad left travel devices is provided at the side of each of the support guides 8a and 8b via freely slidable set frames 9a and 9b. Furthermore, one cylinder C for the slidable operation of the track frame 10 is positioned at an intermediate position between the fitting positions of the support guides 8a and 8b of the track frame 10 immediately under a rotary joint 17 for forming hydraulic pressure between the travel machine table 2 and a turntable 3. Also, a port 24 for connecting an oil passage 23 related to the cylinder C is formed at a level higher than a plane for mounting the rotary joint 17 to the machine table 2.