In this research, we carried out the evaluation of the measurement accuracy for an in-line stereoscopi PIV system with a single camera. Conventional stereoscopic PIV systems use two or more cameras, thus a complex adjustment of camera settings is necessary. We developed a simple stereoscopic PIV systel composed of a single camera, mirrors and a half-mirror. This system is applied to in-line stereogrammeti method, which requires that the two cameras have the same optical axis. In this developed system, howeve one camera is replaced with the mirrors, and a double particle image is separated using the half-mirror.