Wave energy is one of renewable energy resources with great potential. Due to the mechanical and structural simplicity, Oscillating Water Column (OWC) wave energy converter (WEC) is considered to be one of the most promising marine renewable energy devices. However, OWC remains not commercialized mainly due to its complex hydrodynamic performance and uncertainty in wave loads. In the present study, based on potential flow theory and time-domain higher-order boundary element method (HOBEM), a fully nonlinear numerical model is developed and used to investigate the wave-induced force and bending moment on a land-fixed dual-chamber OWC device. The Bernoulli equation is used to calculate the wave force and bending moment. The equation is modified by accounting for the pneumatic pressure in the air chamber and the viscosity effect and then solved using an acceleration-potential method. The numerical model was compared with the experiment carried out in a wave-current flume at the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China, and good agreement between the simulation and experimental results was observed. The horizontal components of wave forces on the two curtain walls of the dual-chamber OWC WEC were found to be much larger than the corresponding vertical components. The seaside curtain wall suffered much larger wave loads in comparison with the inner curtain wall. Therefore, the wave force on the seaside curtain wall is the dominant force. The largest wave-induced bending moment occurs at the joint of device and seabed. The effects of the sub-chamber width ratio and curtain-wall draft on the wave-induced force and bending moment are investigated. The dominant wave force and moment increase with curtain wall draft. And the peak wave loads can be reduced by moving the internal curtain wall close to the seaside curtain wall.