A component mounting system including a component mounter on which multiple component supply units are aligned and detachably mounted, and which is configured to perform a mounting process of mounting a component on a board by collecting the component from the component supply units, based on a production job, the system comprising: a unit exchange device configured to automatically exchange the component supply units within the component mounter; and an exchange control device (80, 59); characterized by the exchange control device configured to control the unit exchange device so that: - the component supply unit required for the mounting process is mounted on the component mounter by allowing a temporary position within a supply area of the component mounter different from a predetermined alignment disposition within the supply area suitable for the mounting process, before the mounting process starts based on a new production job; - the remaining component supply unit excluding the component supply unit mounted during the previously performed production job, out of the component supply units required for the mounting process, is preferentially mounted at a vacant position where the component supply unit is not mounted, as the temporary position, before the mounting process starts; and - the component supply unit mounted at the temporary position is re-mounted within the supply area, based on the predetermined disposition, after the mounting process starts. a unit exchange device configured to automatically exchange the component supply units within the component mounter; and an exchange control device (80, 59); characterized by the exchange control device configured to control the unit exchange device so that: - the component supply unit required for the mounting process is mounted on the component mounter by allowing a temporary position within a supply area of the component mounter different from a predetermined alignment disposition within the supply area suitable for the mounting process, before the mounting process starts based on a new production job; - the remaining component supply unit excluding the component supply unit mounted during the previously performed production job, out of the component supply units required for the mounting process, is preferentially mounted at a vacant position where the component supply unit is not mounted, as the temporary position, before the mounting process starts; and - the component supply unit mounted at the temporary position is re-mounted within the supply area, based on the predetermined disposition, after the mounting process starts. - the component supply unit required for the mounting process is mounted on the component mounter by allowing a temporary position within a supply area of the component mounter different from a predetermined alignment disposition within the supply area suitable for the mounting process, before the mounting process starts based on a new production job; - the remaining component supply unit excluding the component supply unit mounted during the previously performed production job, out of the component supply units required for the mounting process, is preferentially mounted at a vacant position where the component supply unit is not mounted, as the temporary position, before the mounting process starts; and - the component supply unit mounted at the temporary position is re-mounted within the supply area, based on the predetermined disposition, after the mounting process starts.