A compact optical device for augmented reality, the compact optical device comprising: an optical means configured to transmit at least part of image light, output from a real object, therethrough toward a pupil of an eye of a user and to reflect image light corresponding to an image for augmented reality, output from an image output unit, on an inner surface thereof and transfer the image light corresponding to an image for augmented reality to a first reflective unit; a first reflective unit disposed inside the optical means, and configured to reflect the image light corresponding to the image for augmented reality transferred from the inner surface of the optical means by reflection and transfer the image light corresponding to the image for augmented reality to a second reflective unit; and a second reflective unit disposed inside the optical means, and configured to reflect the image light corresponding to the image for augmented reality, transferred from the first reflective unit, and transfer the image light corresponding to an image for augmented reality toward the pupil of the eye of the user, thereby providing the image for augmented reality to the user; wherein the optical means has a first surface which the image light output from the real object enters, and a second surface through which the image light corresponding to the image for augmented reality transferred through the second reflective unit is output, wherein the image light corresponding to the image for augmented reality from the image output unit is reflected on the first surface of the optical means and transferred to the first reflective unit, characterized in that the first reflective unit is disposed between the first surface and the second surface and spaced apart from the first surface and the second surface in order to reflect the image light corresponding to the image for augmented reality toward the second reflective unit, wherein the second reflective unit is disposed spaced apart from the first surface and the second surface inside the optical means, wherein the image light corresponding to the image for augmented reality from the image output unit is transferred to the first surface through the space between the first surface and the second reflective unit inside the optical means and then reflected off from the first surface so that the image light corresponding to the image for augmented reality is transferred to the first reflective unit through the space between the first surface and the second reflective unit inside the optical means, wherein the first reflective unit is a concave mirror having a length less than 8 mm in a widthwise direction thereof, and wherein the second reflective unit has a size smaller than 8 mm. an optical means configured to transmit at least part of image light, output from a real object, therethrough toward a pupil of an eye of a user and to reflect image light corresponding to an image for augmented reality, output from an image output unit, on an inner surface thereof and transfer the image light corresponding to an image for augmented reality to a first reflective unit; a first reflective unit disposed inside the optical means, and configured to reflect the image light corresponding to the image for augmented reality transferred from the inner surface of the optical means by reflection and transfer the image light corresponding to the image for augmented reality to a second reflective unit; and a second reflective unit disposed inside the optical means, and configured to reflect the image light corresponding to the image for augmented reality, transferred from the first reflective unit, and transfer the image light corresponding to an image for augmented reality toward the pupil of the eye of the user, thereby providing the image for augmented reality to the user; wherein the optical means has a first surface which the image light output from the real object enters, and a second surface through which the image light corresponding to the image for augmented reality transferred through the second reflective unit is output, wherein the image light corresponding to the image for augmented reality from the image output unit is reflected on the first surface of the optical means and transferred to the first reflective unit, characterized in that the first reflective unit is disposed between the first surface and the second surface and spaced apart from the first surface and the second surface in order to reflect the image light corresponding to the image for augmented reality toward the second reflective unit, wherein the second reflective unit is disposed spaced apart from the first surface and the second surface inside the optical means, wherein the image light corresponding to the image for augmented reality from the image output unit is transferred to the first surface through the space between the first surface and the second reflective unit inside the optical means and then reflected off from the first surface so that the image light corresponding to the image for augmented reality is transferred to the first reflective unit through the space between the first surface and the second reflective unit inside the optical means, wherein the first reflective unit is a concave mirror having a length less than 8 mm in a widthwise direction thereof, and wherein the second reflective unit has a size smaller than 8 mm.