A packet transmission method for a WPAN that for alleviating traffic concentration in an active period and improving network throughput by controlling packet transmission timing in the active period. A packet transmission method for a wireless personal area network including a coordinator operating with a specific duty cycle and a plurality of devices includes determining, when a packet is generated, whether there is another packet waiting to be sent; determining, if there is no other packet waiting to be sent, whether the network is in an inactive period; setting, when network is in an inactive period, a backoff time; and sending the packet when the backoff time has expired. The packet transmission method controls an initial backoff value adaptively to a duty cycle of the network.