A communication device being adapted to be connected to a plurality of slave station devices (20-1 to 20-n) having two different data transmission rates, which is adapted to generate a transmission permission signal including a transmission start time and a transmission time of data with respect to each of the plurality of slave station devices in a bandwidth update cycle based on a bandwidth request amount from each of the slave station devices and is adapted to notify the slave station devices of the transmission permission signal, the communication device comprising: a bandwidth-update-cycle dividing unit that is adapted to divide the bandwidth update cycle into one slot for each of the data transmission rates based on the bandwidth request amount from each of the slave station devices and a communication quality set for each of the slave station devices; a bandwidth-allocation-amount calculating unit that is adapted to allocate a bandwidth to each of the slave station devices in the slot of the corresponding data transmission rate; and a transmission-start-time setting unit that is adapted to set a transmission start time and a transmission time of data of each of the slave station devices, based on an overhead length of a data frame transmitted by each of the slave station devices, characterized in that the bandwidth-update-cycle dividing unit is adapted to weight the bandwidth request amount ReqWi or ReqWj for each of the slave station devices by using a numerical value MinBWi, or MinBWj relating to a communication quality set for each of the slave station devices, to obtain a sum of the bandwidth request amounts weighted for each of the data transmission rates, and to divide the bandwidth update cycle according to ratios obtained by dividing the sum of each of the data transmission rates by a sum of all data transmission rates; wherein the sum of the bandwidth request amounts weighted for each of the data transmission rates are calculated according to the following recursive formulas: SL = SL + ReqWi × MinBWi, or SH = SH + ReqWj × MinBWj, wherein i is an identifier added to a low-rate slave station device #i; j is an identifier added to a high-rate slave station device #j; MinBWi is a minimum bandwidth set to the low-rate slave station device #i; MinBWj is a minimum bandwidth set to the high-rate slave station device #j; wherein the bandwidth update cycle W is divided between a low-rate slot WSL and a high-rate slot WSH according to the following formulas: WSL = W × SL / SL + SH; WSH = W × SH / SL + SH. a bandwidth-update-cycle dividing unit that is adapted to divide the bandwidth update cycle into one slot for each of the data transmission rates based on the bandwidth request amount from each of the slave station devices and a communication quality set for each of the slave station devices; a bandwidth-allocation-amount calculating unit that is adapted to allocate a bandwidth to each of the slave station devices in the slot of the corresponding data transmission rate; and a transmission-start-time setting unit that is adapted to set a transmission start time and a transmission time of data of each of the slave station devices, based on an overhead length of a data frame transmitted by each of the slave station devices, characterized in that the bandwidth-update-cycle dividing unit is adapted to weight the bandwidth request amount ReqWi or ReqWj for each of the slave station devices by using a numerical value MinBWi, or MinBWj relating to a communication quality set for each of the slave station devices, to obtain a sum of the bandwidth request amounts weighted for each of the data transmission rates, and to divide the bandwidth update cycle according to ratios obtained by dividing the sum of each of the data transmission rates by a sum of all data transmission rates; wherein the sum of the bandwidth request amounts weighted for each of the data transmission rates are calculated according to the following recursive formulas: SL = SL + ReqWi × MinBWi, or SH = SH + ReqWj × MinBWj, wherein i is an identifier added to a low-rate slave station device #i; j is an identifier added to a high-rate slave station device #j; MinBWi is a minimum bandwidth set to the low-rate slave station device #i; MinBWj is a minimum bandwidth set to the high-rate slave station device #j; wherein the bandwidth update cycle W is divided between a low-rate slot WSL and a high-rate slot WSH according to the following formulas: WSL = W × SL / SL + SH; WSH = W × SH / SL + SH.