1. A computer system comprising: a management computer; a self-service portal; and a cloud infrastructure system having physical computers and a storage device, the management computer, the self-service portal, and the cloud infrastructure system being coupled to each other, wherein the management computer includes virtual/non-virtual management information including the identifiers of the physical computers and virtual/non-virtual statuses that show whether the usage modes of the physical computers provided by an infrastructure manager are virtual environments or non-virtual environments, and user manager monitoring item management information including the virtual/non-virtual statuses and monitoring items output by the self-service portal on the basis of the virtual/non-virtual statuses; receives the designation of a physical computer as a monitoring target from the self-service portal; makes a judgment whether the usage mode of the designated physical computer is non-virtual or virtual with reference to the virtual/non-virtual management information; specifies monitoring items to be monitored regarding the designated physical computer with reference to the user manager monitoring item management information; and transmits the specified monitoring items to the self-service portal, and the self-service portal outputs the specified monitoring items.