1. A defect inspection apparatus for inspecting a sheet-like inspection object using a photographed image of the sheet-like inspection object, the photographed image being input from a photographing apparatus, the defect inspection apparatus comprising: at least one processor configured to divide the photographed image of the sheet-like inspection object into blocks each of which has a size of a predetermined number of pixels by a predetermined number of pixels; calculate a longitudinal variance based on pixel values in a longitudinal direction in each block and a lateral variance based on pixel values in a lateral direction in the block; determine whether the block is a defect candidate using the longitudinal variance and the lateral variance as sheet-like inspection object defect determination evaluation values; and determine, based on one of a length and an area of the blocks determined as the defect candidates, whether the sheet-like inspection object has defect.