PURPOSE: To set probability to be coincident with actuality by providing phenomenon number storage means, a probability calculation control means and a probability calculation means, and learning probability that the other phenomenon occurs in accordance with the previously set number of times as against the phenomenon when the new phenomenon occurs.

CONSTITUTION: The phenomenon number storage parts 1 and 2 store the number of the occurrence times of the plural phenomena. The probability calculation control part 3 decides whether probability that the other phenomenon newly occurs is calculated or not in accordance with the number of the occurrence times the specified phenomenon. The probability calculation part 4 calculates phenomenon occurrence probability by the number of times stored in the phenomenon number storage parts 1 and 2. A probability storage part 5 stores phenomenon occurrence probability which the probability calculation part 4 calculates. When the phenomenon newly occurs, probability that the other phenomenon occurs with a period corresponding to the number of times, which is previously set to the phenomenon, is learnt. Thus, the precision of probability can be improved and the time required for execution of calculation can be shortened.