A plurality of pieces of measurement result data measured in a prescribed period is retrieved from blood pressure data stored in a memory. A CPU determines whether at least a plurality of prescribed number of pieces of blood pressure data corresponding to each of the plurality of measurement conditions are present in the retrieved plurality of pieces of blood pressure data. When the CPU determines that at least the plurality of prescribed number of pieces of blood pressure data are present, it calculates an average value of a blood pressure data group that includes the at least the plurality of prescribed number of pieces of blood pressure data, for each of the measurement conditions. The CPU then calculates a correlated evaluation quantity based on correlation of the average values respectively calculated for the measurement conditions.