This dummy substrate is for use in an inline reactive sputtering apparatus. The main unit thereof is made of a rectangular-plate-like frame structure in which an opening portion in a rectangular shape is formed in a metal plate in a similar shape. It is configured such that a contact portion of a carrier with the main unit is covered with the main unit. As a result, even while the sputtering apparatus is in operation, there is no possibility of the occurrence of undesirable situations such as glass cracking, making it possible to significantly increase the number of times the dummy substrate is used. Furthermore, the dummy substrate continues to cover the contact portion with the carrier. Thereby, it is possible to prevent deposition of a substance left in a sputter deposition chamber, especially a compound thin film, on the contact portion of the carrier with the substrate. Therefore, it is possible to prevent undesirable situations such as an abnormal discharge due to the deposition of the compound thin film. As a result of these, it is possible to start (activate) an apparatus that deposits a compound thin film by the sputtering method, retain and modify a deposition condition in the apparatus, and stop (deactivate) the apparatus in a shorter time, and more efficiently and at a lower cost than before.