The AREX Airport Railway Express train is a direct line that starts at Incheon Airport and makes a 43-minute, non-stop journey to Seoul Station. Tickets are priced at 14,800 KRW for Adults.
Likewise, the All Stop train connects Incheon Airport and Seoul Station; however, it makes numerous stops in-between—about 11—and thus, takes longer to arrive into downtown Seoul (56-minutes).
Tickets are priced at 4,250 KRW for Adults, and you’ll also need to place a 500 KRW deposit in addition to the ticket fee. The 500 KRW may be reimbursed by placing your Train card into the Deposit Refund Device when exiting Seoul Station.
You can find out more about the trains’ time schedules at the Airport Express website.