An apparatus and method for detecting defects in a wafer are provided. An optical part is disposed under an inspection stage and radiates infrared light. An image obtaining part detects the infrared light transmitted through the wafer to output an image signal. A conveying part conveys the image obtaining part or the inspection stage in a short side direction of a photographing region of a line sensor included in the image obtaining part, and outputs a pulse signal. A controller counts the pulse signal and outputs a photographing instruction signal controlling the image obtaining part to photograph the wafer whenever the wafer is conveyed in the short side direction of the photographing region of the line sensor toward the image obtaining part by a distance corresponding to the length of short sides of the photographing region. A defect detection part combines each image signal to generate an inspection image.