A boring rig (14) for underground boring for excavating purposes and including a substructure (21, 22), a propulsion device, a stabilizing device (31, 32, 35, 36, 37, 38, 39, 42), and a boring unit (20) having a cutter head (29) and a rotation and forcing device (26), in which the rig has a first direction of general travel and two sideways directions, and in which the boring unit (20) is pivotally attached to the substructure for pivotal movement of the boring unit into an operating direction. The stabilizing device includes horizontal (31, 32) and vertical (35, 36, 37, 38, 39) stabilizing elements that are attached to the substructure (21, 22) in order, in active positions, to be pressed against an adjacent rock face so as to transmit forces from the boring unit (20), that are occurring during boring, to the rock face.