In this paper, the workpiece size measurement system is designed to measure the size (width and height) of a workpiece using the measurement system with a camera. The system consists of a body, a vertical camera movement mechanism, a horizontal camera focus adjustment mechanism, a horizontal illumination device, a vertical illumination device, an infrared sensor, and a control device. To improve the measurement accuracy, camera calibration and image rotation calibration were performed, and image processing was performed using a subpixel algorithm. As a result of measuring the width and height of the block gauges as a reference object using the workpiece size measurement system, the width measurement accuracy was ±0.0041 mm and the height measurement accuracy was ±0.0043 mm. Therefore, it is considered that the designed workpiece size measurement system can measure a workpiece with accuracy less than ± 0.01.