Electrodeposition of Cu on an Au(111)/mica electrode surface coated with a self-assembled monolayer (SAM) of propanethiol has been studied in a potential region comprising the underpotential deposition (UPD). The UPD of Cu and stripping of the deposited Cu took place reversibly through the SAM layer, and furthermore it was found that the SAM was still present on the electrode surface without significant changes in its amount and structure even after repeating Cu deposition/stripping cycles. The Cu adlayer stabilized the SAM completely toward its reductive desorption in an alkali solution, suggesting that a homogeneous Cu adlayer was formed on the entire electrode surface. A surface structure of the resulting electrode is discussed on the basis of these electrochemical results.