Abstract: A glass sheet defect detection device includes a light source and a light reception device which are placed at opposed positions so as to sandwich a glass sheet. The glass sheet has light-transparent surfaces opposed to each other in a thickness direction. The glass sheet is placed between the light source and the light reception device so that the light-transparent surfaces are inclined with respect to a light axis of an optical system of the glass sheet defect detection device at a predetermined angle. Moreover, the light reception device and the glass sheet are placed in such a positional, relationship that a focal length of a lens system of the light reception device is smaller than a distance from a light reception element of the light reception device and the glass sheet.