The present invention relates to: a method by which a small cell having a relatively narrow cell range changes to an active state in an environment in which the small cell is arranged; and a method and a device by which a terminal detects a small cell base station in an inactive state. According to one embodiment of the present invention, provided are a method and a device by which a terminal measures a discovery signal, the method comprising the steps of: receiving a discovery signal from a small cell base station in an inactive state; and measuring the discovery signal on the basis of a reference signal of the discovery signal comprising a primary synchronization signal (PSS), a secondary synchronization signal (SSS) and a cell-specific reference signal (CRS).