Composite materials have been developed to be more light and strong and recently studied for application to large structures such as aircraft and submarines. The composite is made by stacking a number of material layers such as carbon fiber, glass fiber, epoxy resin, titanium, and aluminum. However, the composites in which multiple sheets are laminated have a risk of delamination at each layer during manufacturing process or in-use. In the case of delamination, defects can be detected by ultrasonic inspection among the non-destructive inspection methods. Recently, automated inspection systems have been developed to improve reliability of inspection by using a multi-joint robot. In this study, a multi-joint robotic ultrasonic inspection system was developed and applied to an industrial practice field including a composite manufacturing company. Based on the defect signal obtained by the developed inspection system, the images were obtained by the curvature and plat scan of the system. The defects are identified by fracturing the composite component. These results could lead to increase the reliability and improve the quality competitiveness of the composite materials.