PROBLEM TO BE SOLVED: To provide a practical atrial fibrillation detection system capable of suppressing false positive detection by excluding a normalized pulsation interval related to a predetermined extrasystole not derived from atrial fibrillation. SOLUTION: This is an atrial fibrillation detection system 1 for detecting the presence or absence of atrial fibrillation of a subject, and a pulsation interval measuring means 4 for measuring a pulsation interval of a heart, and a normalized beat from the pulsation interval of the heart. Normalized beat interval calculation means 8 for calculating the beat interval DR (N), and unnecessary extrasystole for excluding the normalized beat interval relating to the unnecessary extrasystole that does not originate from atrial fibrillation from the normalized beat interval data. The unnecessary extrasystole is excluded, and the unnecessary extrasystole is provided with a sinus block excluder, an intervening extrasystole, a continuous ventricular extrasystole, or a two-stage pulse excluder. [Selection diagram] Figure 1【課題】心房細動に由来しない所定の期外収縮に関する正規化拍動間隔を除外して偽陽性の検出を抑制できる実用的な心房細動検出システムの提供。【解決手段】対象者の心房細動の有無を検出する心房細動検出システム１であって、心臓の拍動間隔を測定する拍動間隔測定手段４と、心臓の拍動間隔から正規化拍動間隔ＤＲ(Ｎ)を算出する正規化拍動間隔演算手段８と、正規化拍動間隔データから心房細動に由来しない不要な期外収縮に関する正規化拍動間隔を除外する不要期外収縮除外手段９とを備え、不要期外収縮除外手段９には、洞房ブロック除外手段，間入性期外収縮除外手段，連発心室性期外収縮除外手段若しくは二段脈除外手段を設ける。【選択図】図１
