Measuring system includes controller, transmitter, sensor for measuring blood characteristic, reference photo sensor and mask. Transmitter emits the channel of the blood flow of the blood flow in channel of multiple wavelength from the first side to second side. The sensor provides the channel of blood flow on the second side. The channel of reference photo sensor blood flow is set in the first side. In the first side setting stop mask other than reflected light from light from transmitter to enter reference photo sensor. The controller compensation measured value is measured from sensor from reference photo sensor.