A nondestructive inspection system using millimeter-wave was developed for detection of delamination in IC packages. An open-ended coaxial line sensor was used as a source and also a receiver of millimeter-wave signal that was transmitted into and reflected from the packages. The phase of the reflection coefficient was measured for obtaining the information of the delamination. The package was scanned in two perpendicular directions on a plane parallel to the package. A two-dimensional image was created by using the raw data of the millimeter-wave measurement. The millimeter-wave image showed almost same feature as that of scanning acoustic tomography. The delamination was detected significantly without coupling medium. The millimeter-wave inspection system was proved to be a powerful tool for the integrity assessment of IC packages.