This application provides a method and an apparatus for determining an effective time of a timing advance (TA). The method includes: determining a first subcarrier spacing from M subcarrier spacings, where the M subcarrier spacings are subcarrier spacings of L carriers used by a terminal device, and L≥M≥2; and determining an effective time of a timing advance (TA) of each of the L carriers based on the first subcarrier spacing.