Disclosed is an apparatus for detecting a defective component includes an infrared camera configured to capture an image of a test-target component in a production process, and a processor configured to measure a temperature of the component based on the image captured by the infrared camera and identify that the component of which temperature is out of a range of a reference value is defective. In addition, a database of various causes of defect is established, and an expected cause of defect for a defective component or a retest component is reasoned out from the database based on the measured temperature.