Systems and methods related to a structured illumination (SI)-based inspection apparatus are described. The SI-based inspection apparatus may be capable of accurately inspecting an inspection object in real time with high resolution, while reducing the loss of light. Also described are an inspection method, and a semiconductor device fabrication method including the SI-based inspection method. The inspection apparatus may include a light source configured to generate and output a light beam, a phase shifting grating (PSG) configured to convert the light beam from the light source into the SI, a beam splitter configured to cause the SI to be incident on an inspection object and output a reflected beam from the inspection object, a stage capable of moving the inspection object and on which the inspection object is arranged, and a time-delayed integration (TDI) camera configured to capture images of the inspection object by detecting the reflected beam.