A successive approximation ADC capable of reducing deterioration in AD conversion accuracy due to noise is provided. An AD converter according to an embodiment includes: a DA converter that generates a comparison voltage based on a sampling value obtained by sampling an analog signal, and a successive approximation control signal; a reference voltage generation circuit that generates a reference voltage used for the successive approximation process; a comparator that compares the comparison voltage with the reference voltage and outputs a successive approximation result; a successive approximation processing unit that generates the successive approximation control signal based on the successive approximation result; and a storage unit that stores an expected value of the AD conversion process. The reference voltage generation circuit generates the reference voltage based on the expected value stored in the storage unit.