A performance information monitoring method using computers includes the steps of accepting information on a group relating to a first computer in the first computer; storing the accepted group information in a storage in the first computer; accepting performance information from a second computer in the first computer; comparing performance information of the second computer previously stored in a storage with the performance information received from the second computer in the first computer; judging whether or not the second computer is included in the information of the group when finding a difference between the performance information in the comparison result; and transmitting an instruction to the computer included in the group information to change a performance information collection interval according to the judgment result.