A communication apparatus comprising: a first transmission waiting time determination unit to determine first transmission waiting time which is waiting time before performing first transmission of data, from a first time width, using a first random number; and a retransmission waiting time determination unit to determine, when first transmission of data whose priority is lowest fails, retransmission waiting time which is waiting time before performing retransmission of the data whose priority is lowest, from a second time width which is longer than the first time width, using a second random number, and determine, when first transmission of data whose priority is high fails, retransmission waiting time which is waiting time before performing retransmission of the data whose priority is high, from a third time width which is shorter than the first time width, using a third random number; wherein the first time width is composed of n, n is an integer equal to or greater than 2, slots each of which has a first slot width, the second time width is composed of the n slots each of which has a second slot width which is longer than the first slot width, wherein the third time width is composed of the n slots each of which has a third slot width which is shorter than the first slot width, the first transmission waiting time determination unit selects one of the slots of the first time width using the first random number and determines the time corresponding to the selected slot of the first time width as the first transmission waiting time, and the retransmission waiting time determination unit selects one of the slots of the second time width using the second random number, determines the time corresponding to the selected slot of the second time width as the retransmission waiting time of the data whose priority is lowest, selects one of the slots of the third time width using the third random number, and determines the time corresponding to the selected slot of the third time width as the retransmission waiting time of the data whose priority is high. a first transmission waiting time determination unit to determine first transmission waiting time which is waiting time before performing first transmission of data, from a first time width, using a first random number; and a retransmission waiting time determination unit to determine, when first transmission of data whose priority is lowest fails, retransmission waiting time which is waiting time before performing retransmission of the data whose priority is lowest, from a second time width which is longer than the first time width, using a second random number, and determine, when first transmission of data whose priority is high fails, retransmission waiting time which is waiting time before performing retransmission of the data whose priority is high, from a third time width which is shorter than the first time width, using a third random number; wherein the first time width is composed of n, n is an integer equal to or greater than 2, slots each of which has a first slot width, the second time width is composed of the n slots each of which has a second slot width which is longer than the first slot width, wherein the third time width is composed of the n slots each of which has a third slot width which is shorter than the first slot width, the first transmission waiting time determination unit selects one of the slots of the first time width using the first random number and determines the time corresponding to the selected slot of the first time width as the first transmission waiting time, and the retransmission waiting time determination unit selects one of the slots of the second time width using the second random number, determines the time corresponding to the selected slot of the second time width as the retransmission waiting time of the data whose priority is lowest, selects one of the slots of the third time width using the third random number, and determines the time corresponding to the selected slot of the third time width as the retransmission waiting time of the data whose priority is high.