A computer system and its control method capable of allocating resources to a plurality of users in a balanced manner and ensuring information security between the users even when the plurality of users are made to extensively manage a storage system are provided.The storage system includes: a plurality of resource groups defined by grouping of a plurality of resources; a storage area for storing management information of the plurality of resource groups and association information between the plurality of resources and the plurality of resource groups; and a plurality of user groups defined by grouping of the plurality of users, each of the user groups being allocated to at least one of the plurality of resource groups; wherein based on login of at least one user from among the plurality of users, a management device has the storage system execute operation permitted by an authority granted to the user group, to which the relevant user belongs, on the resource group allocated to the user group.