Transfer to Osaka International airport

How to transfer to Osaka International airpotrt? (landing in domestic airport, needs to transfer to International one

If you mean you arrive at Itami Airport and need to go to Kansai Airport, please refer to this page and select "To/From Kansai Airport" at the drop-down box.

http://www.japan-guide.com/e/e2433.html

Your question is difficult to answer because of the confusing naming of Osaka's airports. As a result, I am not sure which airport you are referring to.

Osaka has two airports. The domestic airport is for historical reasons unfortunately named "Osaka International Airport", but now serves domestic flights exclusively. It is more commonly known as Itami Airport.

Osaka's actual international airport is called Kansai International Airport. It also has some domestic flights.

The following page explains how to travel between the two airports:
http://www.japan-guide.com/e/e2033.html?aFROM=2033_2433

In case you just ask how to transfer between terminals at Kansai Airport, note that the airport has two terminals: Terminal 1 is used by international and domestic flights by established airlines, such as JAL and ANA. A transfer comes without the need of leaving the terminal. Terminal 2 is served exclusively by low-cost carriers such as Peach and Jetstar. Buses connect the two terminals.

Jetstar is using KIX Terminal 1, while Peach Aviation is using KIX Terminal 2.
- Kansai International Airport [KIX]: KIX Terminal 2
http://www.kansai-airport.or.jp/t2/en/

Itami Airport [ITM] is misleadingly but officially still named "Osaka International Airport" despite the two facts that it usually does not handle international flights and that it is located mostly in Hyogo Prefecture rather than Osaka Prefecture.