A wireless access system supporting an unlicensed band and, more particularly, to a method for measuring a channel state and an apparatus for supporting the same. As one embodiment of the present invention, a method for reporting channel state information (CSI) in a wireless access system supporting an unlicensed band may comprise the steps of: receiving an upper layer signal including channel state information-reference signal (CSI-RS) configuration information and channel state information-interference measurement (CSI-IM) configuration information for one or more transmission points (TP) included in a transmission opportunity (TxOP) duration; receiving a physical layer signal including TxOP configuration information that indicates which TP is included in the TxOP duration; measuring the CSI by using a CSI-RS resource and a CSI-IM resource for the TP indicated by the TxOP configuration information, on the basis of the CSI-RS configuration information and the CSI-IM configuration information; and reporting the measured CSI.