韓国の法務省からいただいた回答です。
Dear Inquirer, Thank you for your interest in K-ETA. Regarding your inquiry about the K-ETA application for transfer passengers, please find the answer as below: K-ETA is not required for the transfer passengers who are not entering the Republic of Korea. However, transfer passengers who need to go through the immigration process to recheck their baggage or plan to enter the country are required to get a K-ETA. If you want to apply for K-ETA to go through the immigration process, please enter the postal code ‘22382’ and ‘Gonghangro’ for road name address, and select ‘272 Gonghang-ro Jung-gu Incheon’. Also, please enter the contact number as ‘1577-2600’. If you have any further questions, please feel free to contact us. Best Regards, K-ETA Center null
郵便番号「22382」と道路名住所に「Gonghangro」を入力し、「272 Gonghang-ro Jung-gu Incheon」を選択してください。 また、お問い合わせ番号は「1577-2600」とご入力ください。