A log management system is devised to easily discover improper handling log information by managers. Virtual operation systems (OS) are respectively installed for respective users in a file server constructed as an NAS device. These virtual OS function as virtual NAS. The virtual OS and manager OS exchange information relating to log information via an information exchange part constructed as a kernel. The log information produced in the virtual OS is transmitted to a first log management device via a first communications network, and is also transmitted to a second log management device via a second communications network separated from the first communications network. As a result of the same log information being managed by multiplex management using separate management devices, the system detects whether or not there has been any improper handling of the log information.