A hierarchical transmission digital demodulator capable of stable sync capture and stable demodulation through setting of a demodulation operation in accordance with a reception C/N value. A CNR measuring circuit receives a demodulation output from an arithmetic circuit and measures a reception C/N value. During a period until sync is captured, a carrier is reproduced in accordance with the demodulation output that a modulated wave in a header section and a modulated wave of burst symbol signal. After sync is captured, at an intermediate C/N value the carrier is reproduced in accordance with the demodulation output of the header section, burst symbol signal and QPSK signal and in accordance with output from a logical gate circuit, and at high and low C/N values the carrier is reproduced by setting high a carrier reproduction loop gain of a gain control circuit in accordance with a signal from the logical gate circuit.