In this proposal, we propose the high-resolution neutron diffraction experiments for AFeO2 (A=Cu and Ag) using HRPD. Although CuFeO2 is well known as one of magneto-electric multiferroics and spontaneous spin-lattice coupling systems, the crystal symmetry below the Neel temperature has not been clarified so far. As for AgFeO2, neither magnetic structure nor crystal lattice distortion associated with the magnetic orderings have been found at the present stage. Identification of lattice symmetry is very important for understanding mechanisms regarding spin-lattice coupling and multiferroic phenomena. The main purpose of the experiment is to identify the crystal symmetry below Neel temperature in AFeO2 (A=Cu and Ag) using HRPD. In this experiment, we require the machine time of total 4 days.