This paper presents an agent-based simulation model to analyze performance of organization with heterogeneous members. A hierarchical landscapes model with organizational and personal landscapes is proposed and it puts difference of skills and values into difference of personal landscapes. The use of this model shows that an organization needs to have a certain amount of diverse members to improve the whole organizational utility under the changing environment. This is because while the uniform members stay at a state with higher individual utility even if there are diverse members in the organization, the diverse members discover a new state with higher organizational utility and then take others to that state.