To compactly constitute a lubricating mechanism for lubricating a change gear provided in an excavating apparatus driving device for a ground excavator by means of an appropriate lubricant and to obtain sufficient efficiency of a space.

The change gear 27 provided to the excavating apparatus driving device for the ground excavator is constituted of a clutch mechanism section 36 placed to the upper part of a easing 35 of the change gear 27 and change gear mechanism sections 37 and 38 connected to the clutch mechanism section 36 and provided to the lower part of the clutch mechanism section 36, a speed change hydraulic circuit 48 of the change gear 27 is separated from a main hydraulic circuit on an upper turning body side, at the same time, the lubricant in the change gear 27 is used as a hydraulic oil, and the hydraulic oil governing the pressure thereof by a regulator 54 provided in the inside of the speed change hydraulic circuit 48 is made to act on the clutch mechanism section 36 to make the change-over of the clutch mechanism section 36, at the same time, a portion of drain is dropped from the upper part after the operation of the hydraulic oil to constitute the change gear so as to lubricate the clutch mechanism section 36 and change gear mechanism sections 37 and 38, and the change gear 27 and speed change hydraulic circuit 48 are arranged to a rotary table or a rotary frame bearing the rotary table.