The optical rotary adapter is used with an optical tomographic imaging system for acquiring an optical tomographic image of an object under measurement. The adapter includes a fixed sleeve, a stationary optical fiber supported by the fixed sleeve and having an inclined end face, a stationary collimating lens spaced a given distance from the inclined end face, a mounting cylinder carried rotatably with respect to the fixed sleeve, a rotary optical fiber mounted to the mounting cylinder and having an inclined end face, a rotary collimating lens mounted to the mounting cylinder and disposed with a given distance from the inclined end face, and a rotation actuating device for rotating said mounting cylinder. The central axes of the stationary and rotary optical fibers are offset from or inclined with respect to a central axis of rotation of the mounting cylinder to reduce attenuation of returning light from the object.