A weight sensor is provided with a deforming body, a first strain resistor provided to the outer surface of the deforming body, and a pressing member for applying a load to the deforming body. The deforming body includes a tube section having a tube shape extending along the center axis and surrounding the center axis, and also includes a projection projecting from the inner surface of the tube section. The pressing member moves along the center axis to apply moment force to the tube section. The value of the resistance of the strain resistor changes greatly, and the weight sensor can measure a load with high sensitivity.
