In my content type, I have a text field that allow an illimited number of values.
How do I configure Feeds to import multiple datas in this kind of field?
Feeds Tamper will do this for you.
Feeds Tamper provides a small plugin architecture for Feeds to modify data before it gets saved. Several plugins are available by default and are described in the examples section below. Additional plugins can be added in separate modules or through the issue queue.
One of the default plugins is explode. Just set up a feed tamper to take your multivalued field from your CSV and explode it based on whatever delimiter you fancy. This will import it as multiple field values.