A specific phase position detection circuit of the invention includes: a measurement unit that detects two time positions where a signal level of an analog signal is matched with a preset threshold value, as a first reference position and a second reference position in each cycle of the analog signal, and measures a time length between the first reference position and the second reference position, as a reference time period; a computation unit that computes a time period at a preset rate to the reference time period measured in each previous cycle, as an additional time period in each current cycle of the analog signal; and a detection unit that detects a time position shifted from the first reference position detected in a current cycle by the additional time period computed by the computation unit, as the specific phase position, and outputs a detection signal representing the detected specific phase position. The positions having the substantially fixed positional relations to the peak positions are detectable as the specific phase positions in the respective cycles of an analog signal. The technique of the invention thus enables accurate specification of the peak positions even in the analog signal with varying amplitude.