To provide a trend evaluating device which can estimate a trend with improved trend evaluating accuracy by calculating the relative value from the mean value of time series data set in a standard range and the mean time of time series data set in an evaluating object period.

A standard range deciding means 105 decides a standard range based on the inputted evaluating object time. A mean value calculating means 103 calculates the mean value of occurrence frequency of every evaluating object word in an evaluating object period among the time series data which are accumulated in a time series data accumulator 102. A mean value calculating means 104 calculates the mean value of the evaluating object words which are inputted by an input means 101 in the standard range decided by the means 105 among the time series data accumulated in the accumulator 102 and defines this calculated mean value as the reference value of relative occurrence frequency. Then an output means 108 outputs the words accumulated in a trend accumulator 107 as the results.