A security system in a predetermined area is based on a cooperation of security guards and moving bodies. A time-dependent position of each moving body is predetermined. A security simulation system performs a simulation of the security system to search for an appropriate time-dependent position of each security guard. The security simulation system calculates a rushing time from when an abnormality is detected by a first moving body to when a first security guard arrives at a position of the first moving body, and calculates a security coverage area that can be monitored by the security guards and the moving bodies. An evaluation function increases as the rushing time becomes shorter and as the security coverage area becomes wider. The security simulation system determines the time-dependent position of each security guard such that a value of the evaluation function becomes a predetermined level or higher.