A transmission period determination method for determining a transmission period in an intermittent periodic transmit system where a source node transmits a packet at the transmission period to a destination node by transmitting packets from a source node to a destination node, characterized by transmitting a plurality of training packets at a transmission interval D from the source node to the destination node; and the following steps performed by a transmission period determination device: estimating a training time T required for the plurality of training packets received by the destination node, based on a first training packet received by the destination node during training operation time and on a last training packet received by the destination node during the training operation time; calculating a value of a training metric candidate New_TM based on the training time T; and updating by comparing a value of training metric TM and the value of the training metric candidate New_TM, and if the value of the training metric candidate New_TM is larger than the value of the training metric TM, by setting the value of the training metric candidate New_TM to the value of the training metric TM, changing the transmission interval D, and performing the transmitting again, and if the value of the training metric candidate New_TM equals to the value of the training metric TM or less, by determining the transmission period, wherein the estimating further includes estimating time points T start and T end which are time points for the destination node to receive the first training packet transmitted first by the source node and the last training packet transmitted last by the source node, respectively, and estimating the training time T as T end -T start; and wherein the calculating further includes calculating the value of the training metric candidate New_TM based on a ratio of the training time T and a number Num of training packets received without overlap by the destination node. transmitting a plurality of training packets at a transmission interval D from the source node to the destination node; and the following steps performed by a transmission period determination device: estimating a training time T required for the plurality of training packets received by the destination node, based on a first training packet received by the destination node during training operation time and on a last training packet received by the destination node during the training operation time; estimating a training time T required for the plurality of training packets received by the destination node, based on a first training packet received by the destination node during training operation time and on a last training packet received by the destination node during the training operation time; calculating a value of a training metric candidate New_TM based on the training time T; and updating by comparing a value of training metric TM and the value of the training metric candidate New_TM, and if the value of the training metric candidate New_TM is larger than the value of the training metric TM, by setting the value of the training metric candidate New_TM to the value of the training metric TM, changing the transmission interval D, and performing the transmitting again, and if the value of the training metric candidate New_TM equals to the value of the training metric TM or less, by determining the transmission period, if the value of the training metric candidate New_TM is larger than the value of the training metric TM, by setting the value of the training metric candidate New_TM to the value of the training metric TM, changing the transmission interval D, and performing the transmitting again, and if the value of the training metric candidate New_TM equals to the value of the training metric TM or less, by determining the transmission period, wherein the estimating further includes estimating time points T start and T end which are time points for the destination node to receive the first training packet transmitted first by the source node and the last training packet transmitted last by the source node, respectively, and estimating the training time T as T end -T start; and wherein the calculating further includes calculating the value of the training metric candidate New_TM based on a ratio of the training time T and a number Num of training packets received without overlap by the destination node.