PURPOSE: To provide a noninvasive type biochemical substance measuring instrument which is reduced in size and weight and improved in measurement accuracy.

CONSTITUTION: A biological substance measuring instrument 1 is composed of a saliva sucking port 11a which is a saliva collecting means, a sucking member 11 provided with a saliva sucking port 11a and a reduced-pressure sucking port 11b, and a vacuum pump 20. The main body of the device is constituted of a CPU, storage device, and displaying means. When the saliva sucking port 11a of the sucking member 11 is set so as to cover the opening of the submandibular gland of a patient and the saliva is filtrated with a filtrating material 12, the detection accuracy of a sensor is improved, because such a substance as the interstitial solution which comes out from the gums due to alveolar pyorrhea that hinders the biochemical analysis of the sensor is not mixed in the saliva to be measured. When the amount of a resulted product of the reductive reaction of an enzyme is measured with the sensor, the blood sugar value of the patient can be calculated from the correcting information stored in the storing device. Therefore, a noninvasive blood sugar value measuring instrument can be provided.