Abstract: A relationship index value computation unit 100A that extracts n words from m texts representing contents of free conversations conducted by m patients whose severity of dementia is known, and computes a relationship index value reflecting a relationship between the m texts and the n words, a prediction model generation unit 14A that generates a prediction model for predicting severity of dementia based on a text index value group including n relationship index values for one text, and a dementia prediction unit 21A that predicts severity of dementia of a patient from a text subjected to prediction by applying the relationship index value computed by the relationship index value computation unit 100A from a text input by a prediction data input unit 20 to a prediction model are included, and severity of dementia can be predicted without performing a mini-mental state examination.