Abstract: There is provided a defect detection apparatus including: a light illumination section; a group of lenses including an object lens and a focusing lens; a light splitter section that splits the light passing through the lens group into two beams; a deflecting section; a phase shifting section that shifts the phase of the at least one of the beams from the two beams; a wave combining section that wave combines the two beams phase shifted by the phase shifting section; and an imaging section that captures an optical image of light wave combined by the wave combining section, wherein the object lens and the focusing lens are disposed such that two beams that have passed through the focusing lens are parallel to each other and the main axes of the two beams that have passed through the focusing lens are parallel to each other.