A management apparatus which manages plural information processors, manages information indicating at least one of the information processors, belonging to a first group and at least one of the information processors, belonging to a second group; stores first and second schedule information respectively corresponding to the first and second groups, each schedule information indicating a schedule of a power mode to be set on each information processor belonging to the corresponding group; instructs to change over the power mode based on the first or second schedule information; determines, if the power mode indicated by the first schedule information is different from that indicated by the second schedule information, which of the power modes is to be set with priority; and controls so that the power mode determined to be set with priority is set on the information processor belonging to both the first group and the second group.