It uses the Danish Krone.
One Danish Krone is equivalent to approximately €0.13. Check todays exchange rate here.
Follow this link from Wikipedia to read all about this currency which is also used in Greenland and the Faroe Islands.
Look closely at the photos below and the Kroner notes on the Wikipedia link. Don't they look similar to our Euro? A tour guide on our Walking Tour of Copenhagen told us that the Danish people don't want to join the Euro but the government would like to join. So the notes and the coins that have been designed in recent years have become very similar to the Euro currency!