To prevent the generation of air layer in a contact surface between a skin surface of an organism and a probe.

In this somatometer for optically measuring an organism while transmitting and receiving the light to/from the organism with a probe 7, an optical matching agent is arranged in an interface between a measuring window 6 provided in an upper part of a probe 7, which is integrally provided with a light radiating part 4 for radiating the visible light or the near infrared ray to a body to be examined and a light receiver part 6 for receiving the light so as to optically measure the organism, and the skin surface of a body to be examined so as to prevent the generation of an air layer in the interface between the measuring window 6 and the skin surface. With this structure, measurement error due to the reflection of the light in an interface between the skin and the air and in an interface between the measuring window and the air can be eliminated. Since the interface between the measuring window 6 and the skin can be easily stabilized by existence of the optical matching agent, measuring time can be shortened, and multiple bodies can be measured in a short time.