This paper suggests a visual debugging plaftorm based on the game engine, Unity3D for massive parallel processing routines implemented in CUDA. In general, it is tiresome to debug or check the accuracy of numerical geometry information results calculated in a parallel way by GPU; usually, developers would pick and check each numerical value by rummaging overwhelming lines of seemingly meaningless numbers. This manual process is less productive and time-consuming. Also, it is not easy to produce some continuous movements of geometry information to check the validity of implemented CUDA codes for realtime geometry processing applications. To solve those problems, this paper presents a way to use Unity3D game engine to visually and interactively debug CUDA implementations. Also, some practical test results are presented with discussions on limitations of Unity3D as a CUDA debugging platform.