An apparatus which can objectively assess and display to what extent and to which disease the subject belongs based on the signals of changes in hemoglobin amount measured by the optical measurement apparatus is provided. The disease assessment apparatus comprises the feature extraction unit 15 for extracting features of the hemoglobin waveform, the feature analysis unit 16 and the storage unit 12 for storing features by each disease as database. The disease is assessed by extracting various kinds of feature amounts from the hemoglobin signals of the subject measured by the optical measurement apparatus in the feature extraction unit 15 and by applying multivariate analysis of similarities between feature amounts extracted and feature amounts stored by disease in the storage unit 12. Results of assessment are shown as scores expressing similarity with each disease group in a bar graph.