The purpose of this paper is to propose noninvasive internal bleeding detection method by using ultrasound (US) image processing under US cross-section image. In this study, we have developed a robotic system for detecting internal bleeding based on the blood flow measured by using a noninvasive modality like an US imaging device. Some problems related to the measurement error, however, still need to be addressed. In this paper, we focused on US image processing under US cross-section image, and constructed blood flow measurement algorithm under US cross-section image for internal bleeding detection. We conducted preliminary blood flow measurement experiments using a phantom containing artery model and a manipulator equipped with a US probe (BASIS-1). The results present the experimental validation of the proposed method.