Abstract: A polling period controlling apparatus capable of polling with a period traceable temporal variations of management information values of a managed unit is provided with a polling period calculator 5 which decomposes a sequence of management information values, stored in the sequence memory 4, into the sum of sinusoids with different frequencies to find the maximum frequency and determines the polling period from an inverse of two times the largest frequency. A central controller 2 then compares between the required bandwidth specified by the polling period and a network management bandwidth and, when the former is smaller than the latter, obtains the management information value from the managed unit 11 using the polling period. When the former is greater, the central controller 2 obtains the management information value using the polling period determined from the network management bandwidth.