PURPOSE: To prevent a treated substrate from being contaminated by a contaminant attaching to an untreated substrate by providing a substrate holding device of a substrate transfer device with a holding part for an untreated substrate and a treated substrate.

CONSTITUTION: A substrate transfer device 3 transfers a substrate from a carrier C wherein a plurality of substrates are contained to a substrate carrying robot 6. In the process, an untreated substrate is held by a groove 45a of a holding part 45 of a substrate holding device 16. Thereafter, the substrate is carried to a treatment bath 4 by the substrate carrying robot 6 and a surface treatment is carried out in the treatment bath 4. After the treatment, the substrate carrying robot 6 carries the treated substrate from the treatment bath 4 to the substrate transfer device 3. The substrate transfer device 3 receives the treated substrate and holds it by the groove 46a of the holding part 46. Since an untreated substrate is held by the holding part 45 and a treated substrate is held by the holding part 46 in this way, a contaminant attaching to untreated substrate does not attach to a treated substrate through a holding part, thereby preventing contamination of a treated substrate.