Alignment behavior of a discotic liquid crystalline triphenylene (C8OBT) on substrates coated with self-assembled monolayers (SAMs) of alkanethiol and asymmetrical disulfide was investigated by polarized microscopy. Discotic nematic (ND) and rectangular columnar (Col(r)) phases of C8OBT shows a different alignment behavior depending on the element of SAMs. C8OBT exhibits a fan-shaped texture on an alkanethiol SAM in Colr phase, while it shows a planar alignment on a SAM of asymmetrical disulfide.