Just bought mac mini and the power adapter says clearly “Input 110V – 120V “. I bought it in USA but it would be very strange that apple adapters would not support dual voltage.
I have used converter, anyway after some reading on apple support page I have found that you can use the same power adapter in EU in 220V or even 240V (UK). Then only thing you need is just plug converter from USA plug (3 pin plug) to EU plug (2 pin EU style).
To find out more check this discussion.