A data transmitting and receiving method which is adapted to a demand assignment type of a data transmitting and receiving system comprising a master device that schedules data transmission and reception of a network, a slave device that performs data transmission or data reception on the basis of schedule information periodically output from the master device, and a transmission path that connects the master device and the slave device; the method being characterized by comprising the steps of: transmitting, by the slave device to the master device, a request to be associated in the data transmission and reception network, allowing, by the master device, the association of the slave device into the data transmission and reception network,, scheduling, by the master device, a polling band of a fixed size for requesting a data transmission band by the slave device with respect to a specific number of slave devices for each one cycle, transmitting, to the master device by the slave device, either: a) within a polling band assigned to the slave device, a request for a data transmission band for performing data transmission to the master device according to a retention amount of data to be transmitted to the master device by the slave device; or b) a retention amount of data within a polling band assigned to the slave device, when the data can be transmitted within the polling band assigned to the slave device, and when the retention amount of data cannot be transmitted within the polling band assigned to the slave device, transmitting, to the master device by the slave device, within the polling band assigned to the slave device, a request for a data transmission band for performing data transmission to the master device according to the retention amount of data to be transmitted to the master device by the slave device; scheduling the data transmission band requested from the slave device by the master device; and performing communication in the scheduled data transmission band by the slave device. transmitting, by the slave device to the master device, a request to be associated in the data transmission and reception network, allowing, by the master device, the association of the slave device into the data transmission and reception network,, scheduling, by the master device, a polling band of a fixed size for requesting a data transmission band by the slave device with respect to a specific number of slave devices for each one cycle, transmitting, to the master device by the slave device, either: a) within a polling band assigned to the slave device, a request for a data transmission band for performing data transmission to the master device according to a retention amount of data to be transmitted to the master device by the slave device; or b) a retention amount of data within a polling band assigned to the slave device, when the data can be transmitted within the polling band assigned to the slave device, and a) within a polling band assigned to the slave device, a request for a data transmission band for performing data transmission to the master device according to a retention amount of data to be transmitted to the master device by the slave device; or b) a retention amount of data within a polling band assigned to the slave device, when the data can be transmitted within the polling band assigned to the slave device, and when the retention amount of data cannot be transmitted within the polling band assigned to the slave device, transmitting, to the master device by the slave device, within the polling band assigned to the slave device, a request for a data transmission band for performing data transmission to the master device according to the retention amount of data to be transmitted to the master device by the slave device; scheduling the data transmission band requested from the slave device by the master device; and performing communication in the scheduled data transmission band by the slave device.