Withdrawing money in Sri Lanka is quite easy.
The currency is the Sri Lankan rupee, 230 rupees are approximately 1 euro. ATMs are generally available in every large and small town, and credit card withdrawals are usually free of charge.
If you are planning to travel to more remote regions or regions that are not yet very well developed for tourism, it is still advisable to play it safe and withdraw enough cash in advance.
Alternatively, money can also be exchanged at the airport or at authorized money exchange offices in towns, albeit at a slightly worse, but still reasonable rate.