Mono(6-deoxy-6-thiol) beta -cyclodextrins (beta -CyD-SH) were grown on a Au(111) surface in ethanol solution, and monolayer formation process of which was studied by scanning tunneling microscopy for the first time. At the initial stage, beta -CyD-SH molecules were adsorbed on the Au(111) surface not only randomly, but also partially in a linear ordering. In the following stage, islands were formed and resulted in a uniform monolayer. The observed mechanism is completely different from the model predicted on the basis of the macroscopic result, the Langmuir model. An attractive interaction exists between beta -CyD-SHs, contrary to the prediction by the model. The observed growth processes are quite similar to what was previously observed for lipoamide-beta -cyclodextrin (LP-beta -CyD). However, in the case of beta -CyD-SH, the islands did not grow in size as compared to the case of LP-beta -CyD, and the number of the islands increased to form a uniform monolayer. This characteristic indicates that the interaction strength ratio of CyD-Au to CyD-CyD is larger for beta -CyD-SH than that for LP-beta -CyD.