The zookeeper, identified as Shim, mauled by a 3-year-old male Siberian tiger after the animal escaped from its indoor enclosure into a corridor used by zoo staff, Yonhap news agency reported.
Shim, 52, was rushed to a local hospital shortly after 10 a.m. where he was in serious condition, zoo officials said.
No other injuries were reported.
The tiger was corralled back into its pen at 10:38 a.m. and all visitors were evacuated from the zoo.
Officials did not say how the tiger managed to get out of its enclosure, but that an investigation is under way.