A mounting-waiting process for making a substrate to be transferred into a mounting process wait before the mounting process; and a substrate discharge-waiting process for making the substrate transferred from the mounting process wait before the following process are provided. When transfer of an unmounted substrate into the mounting process and transfer of a mounted substrate from the mounting process to the substrate discharge-waiting process are performed simultaneously, it is detected, by a substrate-arrival detecting sensor for detecting the mounted substrate transferred to the substrate discharge-waiting process and a substrate-continuity detecting sensor for detecting the unmounted substrate continuously transferred following to the mounted substrate, that a plurality of substrates have been transferred into the discharge-waiting process continuously.