A derived electrocardiogram generating system includes: a personal coefficient database which stores personal coefficients specific to a subject, the personal coefficients being acquired from the subject a population coefficient database which stores population coefficients which are average values of conversion coefficients acquired from an unspecified large number of persons belonging to a statistically significant population and an electrocardiograph control portion: which generates a derived electrocardiogram of the subject using the personal coefficients when the personal coefficients are present in the personal coefficient database and which generates a derived electrocardiogram of the subject using the population coefficients when the personal coefficients are absent in the personal coefficient database.
