An electrocardiogram signal processing method and device for extracting a fetus electrocardiogram signal included in a biopotential signal detected from an electrode attached to a mother's body is provided. The electrocardiogram signal processing method for extracting an electrocardiogram signal of a fetus (1b) from a biopotential signal containing electrocardiogram signals of the mother's body (1) and a fetus (1b) inputted through an electrode (E) attached to the mother's body (1) during pregnancy, comprises a reference signal generating step 4 of generating a reference signal for separating/extracting a fetus electrocardiogram signal of a specified induction type according to a beat rate signal inputted from a sensor (S) for detecting the beat rate of the fetus (1b) and a fetus electrocardiogram signal extracting step 5 of separating/extracting the fetus electrocardiogram signal of the specified induction type from the biopotential signal inputted through an electrode (E) according to the reference signal generated at reference signal generating step 4 by a reference system independent component analyzing method.