A low-power transmitting apparatus and transmission method in a wireless personal area network (WPAN). A length of a fragment, a data rate, and a transmission power is selected to transmit a frame with minimum energy consumption in a contention period and a contention-free period. Thus, a quality of service (QoS) requirement for the transmission can be satisfied and the data frame can be transmitted with less energy consumption. Even when the channel status changes, a new transmission criterion suitable for the changed channel status is selected to minimize the consumption of the unnecessary energy. Furthermore, the life span of the network according to the energy consumption under a restricted environment can be lengthened.