A diagnostic parameter calculation method, system and program which detect symptomatically abnormal electrocardiogram data of a patient, using R-R intervals detected from electrocardiogram data collected for a patient to generate a time-series data, then generating a series of partial sets B(j)'s, each B(j) consisting of successive elements starting from the j-th element of the time-series data, and calculating characteristic quantity set (yj, xj) for each B(j), wherein yj is the mean value of all elements, and xj is the mean value of each difference of the first element from each element in the B(j), then, after splitting the (y, x)-plane into lattices, parameters u, v, w are calculated as indices for diagnosis, wherein v is the number of lattices including only one characteristic quantity set, u is the difference subtracted v from the total number of the characteristic quantity sets, and w is the maximum number of characteristic quantity sets included in a lattice.