An optical device is broken down into an optical element made of optical crystal and a holder made of alloy approximated in thermal expansion coefficient to the optical crystal, and the optical element is soldered to or melt bonded to the holder with a piece of solder or glass; the joint area is spaced from the periphery of the optical crystal so that a buffer area, which is spaced from the periphery, is created between the periphery and the joint area; even if cracks and/or scratches have been occurred in an end surface of the optical element, thermal stress is less influential in growing the scratches by virtue of the buffer area, and the optical device keeps the design optical characteristics.