Mechanical collimation commonly uses the photoelectric effect to reconstruct the radiation images. Electronic collimation (i.e., Compton camera) using Compton scattering has been developed to reconstruct radiation images without utilizing mechanical collimators. In general, these kinds of instrument for radiation imaging are used individually, or in order to increase the quality of imaging and radiation detection efficiency, the combination method of each imaging from individual instrument is chosen. In this work, however, we developed the active collimation method including 4π field of view (FOV), which is a new collimation technique using two collimation methods simultaneously without additional detection modules. The 4π FOV active collimation detector consisted of a bismuth germanate (BGO) scintillator detector, a mechanical collimator and five detectors composed of CsI(Na) scintillator. The whole detection module formed a cubic pattern to detect radiation from all incident directions. Therefore, the radiation detection efficiency of the developed device was approximately 7∼8-fold higher than that of the previously developed system.