The present specification provides a method for configuring transmission or reception timing of a wireless device, and a device using the same method. A method for performing uplink transmission by a wireless device in a wireless communication system may comprise a method in which, on the basis that a first serving cell and a second serving cell are included in a particular timing advance group (TAG), and first uplink transmission timing and second uplink transmission timing are different from each other, the uplink transmission is performed on the basis of uplink transmission timing coinciding with reference uplink transmission timing applied to a downlink timing reference cell among the first uplink transmission timing and the second uplink transmission timing.