Abstract: An ultrahigh-speed analog-to-digital converter that does not use optical signals is implemented by means of simple circuit configurations. To achieve this, phase differences between a carrier and modulated signals are detected, the modulated signals having been obtained by modulating the phase of the carrier with an analog signal. Analog-to-digital conversion is then performed by applying binary weighting to the modulation factors of the phase modulations. Alternatively, different relative delays are applied stepwise in 2.sup.n -1 stages (where n is the resolution) between the carrier and the signal that has been phase modulated by the analog signal. The phase of the signals with these delays and the phase of the signal without any delay are respectively compared in 2.sup.n -1 stages. An n-bit digital signal is formed and output on the basis of the results of these comparisons.