To provide an AD conversion circuit that produces a significant noise removal effect while shortening a measurement period.

In an AD conversion circuit 1, a measurement period control section 22 saves measurement data of a plurality of measurement periods allocated in a measurement cycle of repetitive AD conversion in a storage section 21, and controls timings of a ΔΣ modulator 10 and the storage section 21 such that the plurality of measurement periods per measurement cycle are shorter than a noise cycle. An nth-order moving average operation section (first-order moving average operation section 23, second-order moving average operation section 24) performs a moving average process for removing periodic noise on a combination of results of AD conversion over a plurality of measurement cycles.