A substrate processing apparatus having a detecting unit that can detect an abnormality of a substrate such as a crack of the substrate or chipping of the substrate is disclosed. The substrate processing apparatus includes a polishing unit configured to polish a substrate, a cleaning unit configured to clean the polished substrate, a substrate abnormality detection unit configured to detect an abnormality of the substrate, and a substrate transporting mechanism configured to transport the substrate in the order of the polishing unit, the substrate abnormality detection unit, and the cleaning unit. The substrate abnormality detection unit includes an imaging device configured to image the substrate, and an output monitoring unit configured to determine a status of the substrate by comparing a signal obtained from the imaging device with a predetermined threshold.