A power LDMOS device including a substrate, source and drain regions, gates and trench insulating structures is provided. The substrate has a finger tip area, a finger body area and a palm area. The source regions are in the substrate in the finger body area and further extend to the finger tip area. The neighboring source regions in the finger tip area are connected. The outmost two source regions further extend to the palm area and are connected. The drain regions are in the substrate in the finger body area and further extend to the palm area. The neighboring drain regions in the palm area are connected. The source and drain regions are disposed alternately. A gate is disposed between the neighboring source and drain regions. The trench insulating structures are in the substrate in the palm area and respectively surround ends of the drain regions.