A defect inspection apparatus emits light to a test object, detects reflected of scattered light from the test object and detects a defect in the test object The apparatus comprises a temperature-controlled part accommodating section that accommodates parts having a need for controlling a temperature, which is out of a plurality of parts in the defect inspection apparatus. A first temperature measuring instrument measures a temperature in the temperature-controlled part accommodating section; and a temperature control unit controls a temperature of the interior of the temperature-controlled part accommodating section at a prescribed temperature according to the temperature measured by the first temperature measuring instrument. Accordingly, a defect inspection apparatus can efficiently perform temperature control without involving an enlarged size can be achieved.