An AD conversion apparatus comprising: a shift signal generating portion configured to sequentially generate n shift signals ( n is a natural number greater than one) of which amplitudes are different from each other; a compounding portion configured to compound input analog signal and the n shift signals sequentially into n first signals; an AD converting portion configured to execute AD conversion to convert the n first signals sequentially into n second signals; and a signal processing portion configured to process the n second signals into output digital signal, wherein the shift signal generating portion is configured to generate the n shift signals so that each difference between adjacent shift signals differs from natural number multiples of a minimum resolution of the AD converting portion when the n shift signals are arranged according to the amplitudes, characterized in that: the shift signal generating portion is configured to generate the n shift signals so that a difference between a minimum value and a maximum value of the n shift signals is equal to or greater than the minimum resolution of the AD converting portion, wherein the input analog signal is an alternating-current signal, which repeats at a constant interval, one cycle of the alternating-current signal corresponding to the interval, the AD converting portion executing AD conversion in synchronization with the alternating-current signal, the AD conversion apparatus further comprising a shift signal controlling portion configured to control the shift signal generating portion so as to switch the n shift signals every interval of the alternating-current signal, and the signal processing portion processing the n second signals in same phase of each interval of the alternating-current signal into the output digital signal. a shift signal generating portion configured to sequentially generate n shift signals ( n is a natural number greater than one) of which amplitudes are different from each other; a compounding portion configured to compound input analog signal and the n shift signals sequentially into n first signals; an AD converting portion configured to execute AD conversion to convert the n first signals sequentially into n second signals; and a signal processing portion configured to process the n second signals into output digital signal, wherein the shift signal generating portion is configured to generate the n shift signals so that each difference between adjacent shift signals differs from natural number multiples of a minimum resolution of the AD converting portion when the n shift signals are arranged according to the amplitudes, characterized in that: the shift signal generating portion is configured to generate the n shift signals so that a difference between a minimum value and a maximum value of the n shift signals is equal to or greater than the minimum resolution of the AD converting portion, wherein the input analog signal is an alternating-current signal, which repeats at a constant interval, one cycle of the alternating-current signal corresponding to the interval, the AD converting portion executing AD conversion in synchronization with the alternating-current signal, the AD conversion apparatus further comprising a shift signal controlling portion configured to control the shift signal generating portion so as to switch the n shift signals every interval of the alternating-current signal, and the signal processing portion processing the n second signals in same phase of each interval of the alternating-current signal into the output digital signal. the shift signal generating portion is configured to generate the n shift signals so that a difference between a minimum value and a maximum value of the n shift signals is equal to or greater than the minimum resolution of the AD converting portion, wherein the input analog signal is an alternating-current signal, which repeats at a constant interval, one cycle of the alternating-current signal corresponding to the interval, the AD converting portion executing AD conversion in synchronization with the alternating-current signal, the AD conversion apparatus further comprising a shift signal controlling portion configured to control the shift signal generating portion so as to switch the n shift signals every interval of the alternating-current signal, and the signal processing portion processing the n second signals in same phase of each interval of the alternating-current signal into the output digital signal.