In this paper we report a feasibility study of the gamma ray transmission imaging using a double gap resistive plate chamber. The detector consists of two layers of 2mm resistive plate chamber (RPC) gaps with two-dimensional read-out strips of 10mm pitch. Gamma ray transmission images for objects inside a cabinet, using a 10mCi 137Cs isotope, were obtained with a pixel resolution of 5×5mm2. RPC sensitivities for various gamma ray energies were evaluated by the GEANT-based simulations.