The main concept of coded aperture imaging is to increase the SNR while keeping the angular resolution of pinhole imaging. Thus, the coded aperture imaging had been used as a standard technique in the field of astrophysics to detect X-ray or gamma ray from stars. On the other hand, small gamma cameras using pinhole or parallel collimators were applied in the applications of nuclear environment monitoring and nuclear medicine after the development of PSPMT. Adapting the coded aperture to those small gamma cameras using PSPMT was not simple because they were used in near field imaging. There were some factors to be considered before the coded aperture camera was used in near field imaging. In this study, those factors affecting decoding process were investigated and the coded aperture imaging system based on them was set up. Also, coded aperture was modified to fit for real experiment. Using Tc99m source, pinhole images and the coded aperture images were obtained and compared. From the comparison of both systems, feasibility of the coded aperture camera in nuclear medicine or nuclear environment monitoring fields was studied. SNR comparison showed that the coded aperture is favored for concentrated sources and in the environment with high-level background noise. From the experimental results, it was shown that the coded aperture camera does increase the SNR even though some artifacts were shown and its resolution was degraded somehow, which was caused by near field imaging. However, at the expense of small loss of resolution, the coded aperture can be used for reducing radiation dose to patients or making lighter detectors.