The Airport Railroad Express (AREX) is the fastest and most convenient way to get from Incheon International Airport to downtown Seoul. There are two types of trains: the Express Train, which makes no stops between the airport and Seoul Station, and the All Stop Train, which stops at all stations along the way. The Express Train takes approximately 45 minutes and costs 9,000 KRW ($8 USD), while the All Stop Train takes about 53 minutes and costs 4,150 KRW ($3.70 USD). Trains run frequently throughout the day, typically every 10-15 minutes. You can transfer other subways which covers almost every place in Seoul
2) Airport Limousine Bus
The airport limousine bus is another popular option for getting to and from Incheon International Airport. Buses run to and from various locations throughout the city, including major hotels and tourist attractions. Fares vary depending on the route, but generally range from 10,000 KRW ($9 USD) to 16,000 KRW ($14 USD). Buses run every 20-30 minutes, depending on the route.
3) Taxi Cabs
Taxis are readily available at the airport and offer a more comfortable and convenient option for travelers with a lot of luggage. However, they are also the most expensive option. Fares to downtown Seoul typically range from 45,000 KRW ($40 USD) to 75,000 KRW ($66 USD), depending on traffic and time of day. Don't have to worry about the over-charging as drivers are honest.
4) Private Airport Transfer Services
Private airport transfer services offer a more personalized and comfortable option for travelers, with the added benefit of being able to book in advance. Fares vary depending on the service provider and vehicle type, but generally range from 60,000 KRW ($53 USD) to 100,000 KRW ($88 USD) for a sedan or SUV. But if you are first time in Korea then not easy to book in advance.
5) T-money Transportation Card
This card is pre-paid pass card. With this credit card size pre-paid pass, you can ride on Taxi, Subway, Bus, and almost all other vehicles. With this card, you do not have to count Korean strange bills and coins each time. In addition to that they give you discounted price. The card can be purchased and recharged at various locations throughout the city, including convenience stores and subway stations.
