A method for calibration, in a serial fronthaul in which a calibration device and L (L is a natural number equal to or greater than 1) access node(s) (AN(s)) are serially connected, may include: transmitting, by the calibration device, to at least part of the L AN(s), a calibration command message indicating calibration of transmission paths; determining, by the calibration device and the at least part of the L AN(s), time delay values and phase characteristic values of the transmission paths of the at least part of the L AN(s); and transmitting, by the calibration device, to the at least part of the L AN(s), a calibration adjustment message indicating calibration of the transmission paths based on the time delay values and the phase characteristic values of the transmission paths of the at least part of the L AN(s).