Disclosed herein is a method of inspecting defects in a circuit pattern of a substrate. At least one laser beam radiation unit for radiating a laser beam onto an inspection target circuit pattern of a substrate in a non-contact manner is prepared. A probe beam radiation unit for radiating a probe beam onto a connection circuit pattern to be electrically connected to the inspection target circuit pattern in a non-contact manner is prepared. The laser beam is radiated onto the inspection target circuit pattern using the laser beam radiation unit. The probe beam is radiated onto the connection circuit pattern using the probe beam radiation unit, thus measuring information about whether the probe beam is diffracted, and a diffraction angle. Accordingly, the method can solve problems such as erroneous measurements caused by contact pressure and can reduce the time required for measurements.