"Yes, we will appeal [the ruling] this morning," Le Pen said on the BFMTV broadcaster.
The RN politician added that the examining magistrates were trying to "destroy the key opposition party of France."
"This is happening without any respect for any legal criteria, which would have allowed this kind of seizing. This is a real terrorist attack on democracy," Le Pen stressed.
Le Pen also officially rejected all accusations against the party.
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On Sunday, the politician pointed out that the examining magistrates decided to seize that sum as part of the investigation, opened in December 2016, into the RN using EU funds to pay assistants, who worked only for the party, not for the European Parliament.
In June, the Court of Justice of the European Union backed the European Parliament's decision to fine RN almost 300,000 euros, or roughly $347,000, for hiring parliamentary aides and failing to prove their effectiveness.