PURPOSE: To provide a device which can predict data as a guide to investment, etc., by accurately grasping a flow of the market prices of market transaction.

CONSTITUTION: This device consists of the input part 2 consisting of an input part 2 for the time-series data and a keyboard 2b, the processing part 3 consisting of an arithmetic part 4 which makes the center of variation of the inputted data into a smooth continuous line by spline function calculation, an arithmetic part 5 which calculates the probability of the variation of the data as an upper and a lower limit line about the center line, an arithmetic part 6 which calculates a prediction line successively to the calculated center line by Tayor expansion on the basis of the spline function calculation, an arithmetic part 7 which calculates an upper and a lower limit prediction line for the prediction line successively to the upper and lower limit lines calculated by the arithmetic part 5, a chart setting part 8 which charts the data of the respective arithmetic parts on a chart, and an index setting part 9 which inputs the variation of the flow to the area consisting of the center line of the set chart and the upper and lower limit lines, and the output part 10 which displays them at a display part 10a and a printer part 10b.