Abstract: Penetration quality detection is a traditional method to detect the weld quality of the H-beam. As a new penetration quality detection technique, the phased array ultrasonic detection (PAU) is also applied in this area. To make PAU detection faster and more stable, a bilateral inspection scanning mechanical device for H-beam PAU detection is proposed in this paper. This scanning structure device is designed with compact structure, and can scan and evaluate the weld quality of both sides of the weld component. By adjusting the stop wheel group, it can walk stably and accurately. The rubber handle is configured at the center of the device, which can be easily used by one person. With only one person controlling the proposed device, the PAU detection time could be greatly reduced. The scanning results of this device is compared with traditional human inspection results, which proves the reliability of the design.