An measuring instrument for a physiological heat quantity emitted from a human body includes a heat flux sensor, and a calculator. The heat flux sensor includes a sensor main body portion and a moisture absorbing member. The sensor main body portion has multiple through holes penetrating through the sensor main body portion from a first surface to a second surface. The sensor main body portion is disposed on a human body such that the first surface is adjacent to the human body when in use, and outputs a sensor signal according to a heat flux passing through the sensor main body portion from the first surface toward the second surface. The moisture absorbing member is stacked on the second surface of the sensor main body portion. The calculator calculates the physiological heat quantity based on the sensor signal.
