The invention relates to a radial horizontal drilling device. A device assembly has a cylindrical shape, the upper part of the device assembly is fixed in a sleeve by an anchoring head, the lower part of the device assembly adjusts a horizontal azimuth angle for radial drilling through a ground control system; the center of the device assembly is provided with a through guide hole, the upper axis of the guide hole is coincide with the axis of the device assembly, and the lower axis of the guide hole is vertical to the axis of the device assembly; a continuous pipe is connected with a high-pressure hose by a pipe connector and the high-pressure hose passes through the guide hole to be connected with a spray gun; and the device assembly can be used in combination with the prior common equipment to complete all construction work with only one time of lifting and lowering in a whole working process, thereby improving working efficiency and reducing cost. The device is suitable for various oil layers and can realize a radial aperture up to 60 millimeters and a length of a horizontal radial well section of 100 meters. In addition, the device can improve oil drainage area and is suitable for improving yield and extraction of low permeability oil and gas reservoirs, old oil deposits and coal bed gases.