A method of verifying whether an inspection unit, capable of inspecting a defect of an inspected body, in an inspection system has a fault, the method comprising: providing a verification reference body formed on a frame attached to the inspection system, the verification reference body comprising: first verification target including a flat plate having a flat area capable of indicating a height reference for verifying light radiated from the inspection unit, a reference plane for measuring height of the inspection unit and a gray level; second verification target including at least two fiducial markers (322a, 322b, 322c) indicating at least two positions for verifying an accuracy of movement of the inspection unit; and third verification target having a predetermined height for verifying an accuracy of height measurement of the inspection unit; positioning the inspection unit over the verification reference body; obtaining image data of the first verification target through the inspection unit; verifying whether the inspection unit has a fault in an accuracy of an amount of light, setting of the reference plane, and a movement amount of a pattern of the inspection unit based on the image data of the first verification target; obtaining image data of the second verification target through the inspection unit, the image data of the second verification target corresponding to each of the at least two fiducial markers (322a, 322b, 322c); verifying whether the inspection unit has a fault in the accuracy of movement by comparing the positions of the at least two fiducial markers (322a, 322b, 322c) in the obtained image data of the second verification target with predetermined reference data; obtaining image data of the third verification target through the inspection unit; verifying whether the inspection unit has a fault in the accuracy of height measurement by comparing the obtained image data of the third verification target with predetermined reference data; and generating a verification result indicating whether the inspection unit has a fault. first verification target including a flat plate having a flat area capable of indicating a height reference for verifying light radiated from the inspection unit, a reference plane for measuring height of the inspection unit and a gray level; second verification target including at least two fiducial markers (322a, 322b, 322c) indicating at least two positions for verifying an accuracy of movement of the inspection unit; and third verification target having a predetermined height for verifying an accuracy of height measurement of the inspection unit; positioning the inspection unit over the verification reference body; obtaining image data of the first verification target through the inspection unit; verifying whether the inspection unit has a fault in an accuracy of an amount of light, setting of the reference plane, and a movement amount of a pattern of the inspection unit based on the image data of the first verification target; obtaining image data of the second verification target through the inspection unit, the image data of the second verification target corresponding to each of the at least two fiducial markers (322a, 322b, 322c); verifying whether the inspection unit has a fault in the accuracy of movement by comparing the positions of the at least two fiducial markers (322a, 322b, 322c) in the obtained image data of the second verification target with predetermined reference data; obtaining image data of the third verification target through the inspection unit; verifying whether the inspection unit has a fault in the accuracy of height measurement by comparing the obtained image data of the third verification target with predetermined reference data; and generating a verification result indicating whether the inspection unit has a fault.