1. An access right management method for use in a computer system comprising a first storage system, which includes hard disk drives configuring a first logical unit managed by a first management computer coupled to the first storage system storing first management authority information, a second storage system, which includes hard disk drives configuring a second logical unit managed by a second management computer coupled to the second storage system storing second management authority information, and a third management computer coupled to the first management computer and the second management computer, storing resource correspondence information, which third management computer manages the first logical unit and the second logical unit as storage resources via the first management computer and the second management computer, said method comprising: the first management computer managing the first logical unit as a first management resource based on the first management authority information indicating management authorities of a plurality of administrators to the first management resource, the second management computer managing the second logical unit as a second management resource, based on the second management authority information indicating management authorities of the plurality of administrators to the second management resource, the third management computer managing the storage resources based on the resource correspondence information, which indicates correspondences between the storage resources including the first logical unit and the second logical unit and management computers including the first management computer and the second management computer, the third management computer receiving a management authority update request identifying at least one certain storage resource which is one or more of the storage resources and a certain administrator which is one or more of the plurality of administrators, the third management computer selecting one of the first management computer and the second management computer, which manages the at least one certain logical unit associated with the at least one certain storage resource, and sending an update request of a management authority of the certain administrator about the at least one certain logical unit to the one of the first management computer and the second management computer, based on the resource correspondence information, and one of the first management computer and the second management computer, which receives the update request, updating the one of the first management authority information and the second management authority information about the at least one certain logical unit.