Characteristics of a fixed terminator of oscillating water column are described in this paper. It is one of the most promising wave power absorbers, as well as a floating-body-type such as Salters Duck, performances of which were shown in the previous papers. The experimental data both in regular and in irregular waves are compared with calculations based on a linear water wave theory with equivalent floating body approximation. The calculations agree very well with experiments in case of deep water depth and low frequencies. The ability to absorb wave energy is as excellent as Salters Duck both in regular and in irregular waves.