The invention discloses a direction-adjusting device for an open-type full-section hard rock tunneling machine. The direction-adjusting device comprises a main beam, two support boots and a saddle tree, wherein guide rails are arranged on the two sides of the main beam; the two support boots are positioned on the two sides of the main beam; an upper support boot oil cylinder and a lower support boot oil cylinder are arranged on each support boot through a spherical hinge; an upper support boot oil cylinder shaft and a lower support boot oil cylinder shaft are respectively connected between the upper support boot oil cylinders and the lower support boot oil cylinders of the two support boots; the saddle tree is arranged on the guide rails and can move forwards and backwards relative to the guide rails; the two sides of each upper support boot oil cylinder are hinged with the saddle tree by torque oil cylinders; and the upper support boot oil cylinder shaft is connected with the saddle tree through a mutually rotated cross pin shaft structure. After adopting the direction-adjusting device, the open-type full-section hard rock tunneling machine can realize horizontal, vertical and torsion control and adjustment in a tunneling process of the tunneling machine rapidly, accurately and reliably.