A stationary strawberry harvesting robot integrated with a movable bench system was developed. In the system, it is possible to recognize the movable bench individually by attaching a radio frequency identification (RFID) tag, for example. Therefore, it is believed that proper cultivation management, based on growth information of each movable bench, can lead to stable production of high-quality strawberries. In this study, by focusing on sugar content as one instance of growth information that can affect the quality of the fruit, we developed a system for measuring sugar content by a stationary strawberry-harvesting robot. In this system, to consider the posture of the robot-harvested strawberries that were gripped by the peduncle, the size of the strawberry, and the gradient of the sugar content in the fruit, the distance between the fruit equator and the near- infrared spectrometer is controlled to be constant. Estimation of the fruit posture, the equator part in the fruit, and the distance between the equator and the near-infrared spectrometer is performed by image processing based on a red-green-blue (RGB) image and a depth image captured by a RGB-depth sensor. When the accuracies of the sugar content measured by this system and that by manual measuring were examined and compared, the corresponding root-mean-square errors (RMSEs) were 0.80 Brix % and 0.75 Brix %, respectively, which were comparable.