Measurements by use of a conventional caliper process require skills and experiences. Further, since different pregnant women gain and keep fats in their bodies in different ways, results of measurements of their body fats vary. To overcome the inconvenience, there is provided a system for measuring a percent body fat or a total body fat by a bioelectrical impedance method, which comprises first input means, second input means and computation means, wherein personal data of a patient such as a height and a body weight is input into the first input means, a weight of a fetal part is input into the second input means, and the computation means computes a percent body fat or a total body fat by subtracting the body weight input into the second input means from the body weight input into the first input means. Further, to overcome the inconvenience, there is provided a system for measuring a percent body fat by a bioelectrical impedance method which comprises first input means, second input means and computation means, wherein personal data of a patient such as a height and a body weight is input into the first input means, a weight of a fetal part is input into the second input means, and the computation means computes a percent body fat by subtracting the body weight input into the second input means from the body weight input into the first input means.