Measuring subcutaneous fat thickness provides valuable information regarding human health. The thickness is usually measured by magnetic resonance imaging or by ultrasonography; however, the equipment is expensive and limited to large medical institutions. In this study, we propose a simple method in which an ultrasonic pulse is shot into the skin; a reflected wave from a boundary between the subcutaneous fat and muscle is detected, which allows the thickness to be measured. The detection time of the reflected wave is calculated by a cross-correlation method with the aid of a modeling technique of the reflected wave, and the subcutaneous fat thickness is estimated from the detection time. The proposed method was applied to the measurement of the subcutaneous fat thickness of the anterior thigh and the abdomen. The thickness estimated with the proposed method was compared with that measured with a B-mode ultrasonic image. The differences in the thickness were less than or equal to 0.90 mm in the thigh and 2.0 mm in the abdomen when the thickness was less than 19 mm. However, the differences became slightly large when the thickness was around 30 mm or more. These values corresponded to the thickness of the abdomen of an overweight person. The proposed method could provide an inexpensive way to measure subcutaneous fat thickness. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.