One person has been arrested, police said in a statement.
The attack occurred near Seohyeon station, an area about 20 km (12.43 miles) from Seoul that has a large department store and other shops and where many commuters live.
Police said 12 of the victims had been hospitalised.
The motive for the attack was not immediately clear.
The incident comes just days after another rare stabbing attack in Seoul in which one person was killed and three others wounded.
(Reporting by Hyonhee ShinEditing by Ed Davies and Bernadette Baum)

Police control access to the scene of a stabbing rampage at a department store adjacent to Seohyeon Station in Seongnam, just south of Seoul, South Korea, 03 August 2023. According to local Police, 13 people are injured after a man drove into a group of them and later stabbed several other around. EPA-EFE/YONHAP SOUTH KOREA OUT