To provide a measuring cycle variable type measurement control system capable of simplifying the change of the change judgment reference value of the measuring cycle of field equipment and the change of the value of a measuring and communicating cycle, and fixing a useless time L even at the time of changing the measuring cycle.

Host control equipment 1A transmits a communication request TX1N to field equipment (2A) in measuring cycles T1 and T2 designated according to the results of cycle change judging means (3A/3B). The field equipment 2A predicts a timing time T when a communication request is issued to the destination of its own station the next time from the timing in which a communication request TX1(N-1) is issued to the destination of its own station the last time and the measuring cycles T1 and T2 corresponding to a state register 31B which stores the results of the cycle change judging means (3A/3B), and starts a CPU 23 prior to the time T only by a measuring time τ1 of measured variables mes(N) so that the measured variables mes(N) can be measured by a sensor part 26, and receives the communication request TX1N, and makes a reply response TX2N, and stops the CPU 23.