An apparatus is provided which allows a subject to determine by himself/herself whether or not he/she is apt to develop a deep-vein thrombosis in a region of a lower limb in a simple manner. A variation between the bioelectric impedance values measured respectively before and after a posture change is compared with a reference value. The posture change includes a bending and stretching exercise, a bending and stretching in knees in a seated position and a repeating of standing-up and sitting-down motion. Alternatively, a blood storage capacity of the lower limb region may be estimated from a gradient of bioelectric impedance represented by a variation thereof per unit time to determine whether or not the subject is apt to develop deep-vein thrombosis in the lower limb region.