An optical rotary adapter suitable for an optical tomographic imaging system for acquiring an optical tomographic image of an object under measurement, said optical rotary adapter rotatably connecting optical fibers (FB1, FB2) guiding measuring light to said object under measurement and guiding reflected returning light from said object under measurement, said optical rotary adapter comprising: a fixed sleeve, a stationary optical fiber fixedly supported by said fixed sleeve and having on one end thereof an inclined end face inclined a given angle (θ1) with respect to a plane perpendicular to a central axis of said stationary optical fiber, a stationary collimating lens spaced a given distance from said inclined end face of said stationary optical fiber, a mounting cylinder carried rotatably with respect to said fixed sleeve, a rotary optical fiber fixedly mounted to said mounting cylinder so as to be disposed opposite said stationary collimating lens and having an inclined end face inclined a given angle (θ2) with respect to a plane perpendicular to a central axis of said rotary optical fiber, and a rotary collimating lens fixedly mounted to said mounting cylinder and disposed between said stationary collimating lens and said rotary optical fiber with a given distance from said inclined end face of said rotary optical fiber, wherein the optical rotary adapter further comprises rotation actuating means configured to rotate said rotary optical fiber and said rotary collimating lens by rotating said mounting cylinder when the measuring light is irradiated and the returning light is acquired, the rotary adapter further comprises ferrules (41, 49) and holders (43a,51a) for each of said stationary optical fiber and rotary optical fiber respectively, said stationary optical fiber and said rotary optical fiber are supported at a center of their respective ferrules (41, 49) and the respective ferrules (41, 49) are held by respective holders (43a, 51a), the respective holders (43a, 51a) comprise a flange section (43b, 51b), a straight tubing section (43c, 51c) having a through-hole (43d, 51d) holding the respective ferrules (41,49) at the center thereof and the flange section (43b, 51b) having an external end face inclined a given angle (φ1, φ2) with respect to the central axis of rotation of the mounting cylinder, and the inclined external end face of the flange section of the respective holders (43a, 51a) is fixedly mounted to said fixed sleeve and said mounting cylinder so that said central axes of said stationary optical fiber in the holder and said rotary optical fiber in the holder are inclined with respect to a central axis of rotation of said mounting cylinder to reduce attenuation of said returning light. a fixed sleeve, a stationary optical fiber fixedly supported by said fixed sleeve and having on one end thereof an inclined end face inclined a given angle (θ1) with respect to a plane perpendicular to a central axis of said stationary optical fiber, a stationary collimating lens spaced a given distance from said inclined end face of said stationary optical fiber, a mounting cylinder carried rotatably with respect to said fixed sleeve, a rotary optical fiber fixedly mounted to said mounting cylinder so as to be disposed opposite said stationary collimating lens and having an inclined end face inclined a given angle (θ2) with respect to a plane perpendicular to a central axis of said rotary optical fiber, and a rotary collimating lens fixedly mounted to said mounting cylinder and disposed between said stationary collimating lens and said rotary optical fiber with a given distance from said inclined end face of said rotary optical fiber, wherein the optical rotary adapter further comprises rotation actuating means configured to rotate said rotary optical fiber and said rotary collimating lens by rotating said mounting cylinder when the measuring light is irradiated and the returning light is acquired, the rotary adapter further comprises ferrules (41, 49) and holders (43a,51a) for each of said stationary optical fiber and rotary optical fiber respectively, said stationary optical fiber and said rotary optical fiber are supported at a center of their respective ferrules (41, 49) and the respective ferrules (41, 49) are held by respective holders (43a, 51a), the respective holders (43a, 51a) comprise a flange section (43b, 51b), a straight tubing section (43c, 51c) having a through-hole (43d, 51d) holding the respective ferrules (41,49) at the center thereof and the flange section (43b, 51b) having an external end face inclined a given angle (φ1, φ2) with respect to the central axis of rotation of the mounting cylinder, and the inclined external end face of the flange section of the respective holders (43a, 51a) is fixedly mounted to said fixed sleeve and said mounting cylinder so that said central axes of said stationary optical fiber in the holder and said rotary optical fiber in the holder are inclined with respect to a central axis of rotation of said mounting cylinder to reduce attenuation of said returning light.