It is recognized that an offset is added to a measurement value shown by a weight scale. In a case where a measurement value, shown by a body weight scale, has decreased from a first reference value by more than a first threshold, an offset determining section determines whether or not a difference between the measurement value and a second reference value is greater than a second threshold. In a case where the offset determining section determines that the difference between the measurement value and the second reference value is greater than the second threshold, the offset determining section stores the measurement value as a candidate second reference value.
