A part of the image input from a fingerprint sensor (S1) is cut out (S3), and a fundamental frequency is calculated by using second-order linear predictive analysis (S5). A total value S of the fundamental frequencies in a direction x and a direction y is calculated so as to be used as a grading scale of fineness in texture (S7). A prepared threshold is compared with the grading scale S obtained at S7, and the fineness in texture of a skin condition is evaluated in three grades (S9 to S17). Further, a ratio of the fundamental frequency of the subject image in the direction x to the fundamental frequency in the direction y is calculated so as to be used as a grading scale relating to texture running (S19). Similar grading scales are obtained by rotating the image, and the texture running is determined into two grades based on the grading scales (S31 to S35). Results of determining the fineness in texture and the texture running are displayed on a display screen (S37).