To combine the function of a rod holder with a self-locking function of clamp-holding rods by their own weight to prevent fall of the rods, and a function of gripping the lower rod and turning the rod on the upper side of a screw joint by a spindle or the like to unscrew mechanically.

In a rod holder for holding boring rods 9, 10 of an excavating device for excavating the ground, two sets of chucking pieces 5 are mounted to tip fittings of piston rods of two sets of hydraulic cylinders respectively by pins 6, and the tail parts of the hydraulic cylinders are opposedly mounted to shafts so that the chucking pieces 5 are on the boring rod side. When the rods 9, 10 are going to fall by their own weight due to the rotation of the hydraulic cylinders and chucking pieces 5 around the shafts as rotating shafts, the chucking pieces 5 come in contact with the rods 9, 10, and the rods 9, 10, the chucking pieces 5 and the hydraulic cylinders form a bridge to prevent fall of the rods 9, 10. Oil pressure is applied to the hydraulic cylinders to grip the rods 9, 10 and to separate the rods 9, 10.