Provided are a surface inspection apparatus and method capable of detecting foreign materials on the surface of a substrate, and a slit coater having the surface inspection apparatus. In the surface inspection apparatus, a slit lighting unit irradiates slit-shaped light. An optical system splits the slit-shaped light into two beams traveling along two different paths, is incident upon a subject, and extracts an interference image caused by combination of the two beams reflected from the subject. An imaging device captures the interference image to output an image signal. An analysis unit acquires a luminance value of the image signal, analyzes the luminance value in real time, and determines whether or not foreign materials are present.