A leg movement acquisition unit 1 continuously acquires leg movements of a sleeping subject. An apnea detection unit 2 detects whether or not the subject is in a state of apnea. A movement analysis unit 3 determines whether or not the detected leg movement satisfies previously determined conditions. These previously determined conditions include at least the following conditions (a) to (d): (a) The duration of leg movement is within a previously determined range (b) intensity of leg movement is a previously determined value or greater (c) leg movements satisfying conditions (a) and (b) continue for a previously determined number of times within a previously determined duration and (d) the leg movement is not movement from immediately before to immediately after an apnea state that has been detected by the apnea detection unit. A coefficient calculation unit 4 calculates a coefficient based on the number of times of leg movement that satisfied the previously determined conditions. An output unit 6 outputs the coefficient or a determination result based on the coefficient.
