The KASINICS (KASI Near Infrared Camera System) is a ground-based Near-Infrared (NIR) imaging instrument developed by the Korea Astronomy and Space Science Institute (KASI). In this paper, we report the test results of the KASINICS camera optics system which is comprised of a 1-1 Offner relay. We measure that the surface RMS fluctuations of the Offner mirrors are at the level of $10^{-1}-10^{-2}$ of the target wavelengths, showing that the mirrors are sufficiently smooth for NIR observations. The alignment of the Offner optics system has been checked too. Our ray-tracing simulations find that the image quality should not degrade more than the pixel size of the KASINICS ($40{mu}m$), if a de-centering or a tilt of the Offner mirrors are within 5mm, or $2.5^{circ}$. Our measurement shows that the de-centering or the tilt of the Offner mirrors are less than 1 mm or $0.5^{circ}$, assuring that the KASINICS image quality are not affected by the alignment errors. We have also measured that the optics resolution is $20{mu}m$ and it does not degrade more than 10% over the detector surface area of 14.3 mm ${/times}$ 14.3mm. Overall, we conclude that the KASINICS optics system satisfies the design requirements for NIR imaging observations.