The invention relates to underground drilling equipment for petroleum, in particular to an underground horizontal bore drilling tool used for petroleum drilling, which can finish boring a steel sleeve wall and cement or rock by descending once. The underground horizontal bore drilling tool comprises an executing mechanism and a power source connected with the executing mechanism in a sealing way,wherein the executing mechanism is divided into an inner layer, an intermediate layer and an outer layer, and comprises a drilling tool and a guide device; the drilling tool is used for drilling the steel sleeve wall; the guide device is used for boring a cement layer and the rock; and the drilling tool and the guide device are driven to perform reciprocating movement by a positioning hydraulic cylinder so that horizontal boring of the steel sleeve wall, the cement layer and the rock can be finished by descending once. Therefore, underground horizontal boring efficiency is greatly improved; the power source provides power for the executing mechanism through an oil tube; and seal between the oil tube and a sealing connecting piece is good so that a motor, a battery and an electric wire do not need to be sealed specially. The equipment of the invention has the characteristics of simple structure, convenient operation and low cost.