Provided are a method for managing a beam performed by a terminal in a wireless communication system and a device using the method. According to the method, the terminal performs a power saving operation on a first cell and receives a PDCCH through a second cell, wherein the PDCCH requests to measure a reference signal transmitted aperiodically in the first cell. The reference signal is received at a particular time for a DRX cycle related to the power saving operation. The terminal generates beam related information to be used in the first cell by measuring the reference signal in the first cell.