Provided are a method and system for providing a sleep state in a device accessible to a wired or wireless network. Provided are a method and a system, which dynamically determine the optimal parameter in a sleep state depending on a network characteristic in providing the sleep state to a network-accessible terminal, and thus reduce the period of an active state of the network-accessible terminal, thereby considerably decreasing power consumption. Provided are a method and a system, which do not unnecessarily use a clock in an active state by selecting the optimal clock according to a purpose of transiting from the sleep state to the active state, and thus reduce the period of the active state of the network-accessible terminal, thereby considerably decreasing power consumption.