Excavating device for underground diaphragm wall capable of releasing/preventing deflection of top guide wheel

The present invention provides an excavation device for an underground diaphragm wall capable of releasing/preventing deflection of a tip guide wheel, the excavation device being provided with: track frames, track cross-linking beams, and cross-frame support beams which are each fixedly provided to a pair of left and right track frames in the longitudinal direction of a track, and on which cross-guiding parts are fixedly provided; a transverse frame which is fixedly provided with a transverse sliding part and which freely travels along the transverse frame support beam by means of the sliding of the transverse sliding part on the transverse guide part; one end of the transverse moving hydraulic cylinder is fixed on the transverse moving frame, and the other end of the transverse moving hydraulic cylinder is fixed on the transverse moving frame supporting beam, so that the transverse moving sliding part freely moves along the transverse moving guide part; the swinging hydraulic cylinder comprises a fixed end a