In wireless network communication, the present invention provides a method of checking whether information on a request for a mode change is received for a prescribed channel time in a manner that a device configuring a network enters a power save mode in the course of not performing data transmission/reception and that a modem enters an awake state from a sleep state for the prescribed channel time. And, the prescribed channel time is determined to correspond to a time for transmitting a beacon. According to one preferred embodiment of the present invention, a modem of a device in a power save mode enters an awake state for a channel time period for broadcasting a beacon and then checks whether information on a power management mode change is received. If the information does not exist, a sleep state is reentered. If the power management mode change information is received, a power is managed by performing data transmission/reception in a manner of switching to a normal mode.