An optical structure for acquiring a fingerprint image with high resolution and minimum distortion is provided. The optical structure includes a prism configured to comprise an input surface to which light is irradiated, a contact surface formed horizontally to be in contact with a finger, and an output surface through which the light that has been irradiated to the input surface and reflected from the finger in contact with the contact surface passes; a lighting unit configured to emit a beam to the input surface of the prism; a reflector unit configured to reflect a fingerprint image passing through the output surface of the prism; a lens unit configured to comprise two or more lenses, each being configured to receive the fingerprint image reflected from the reflector unit; and an image sensor on which the fingerprint image passing through the lens unit is formed.