"My client does not agree with the conviction. We believe that he should be found not guilty," said Theo Jansen, De Wit's lawyer.
"You could say that my client was clueless. But he disputes that his intent was to do damage and it has not been proven that great damage was done."
No date has been set for the appeal, but Jansen expects the court will wait until September.
De Wit was charged with spreading data via a computer network with intent to cause damage, a crime punishable by four years in prison and a maximum fine of about €45,000 (£27,860).The prosecutor asked the court for 240 hours of community service.
De Wit used a worm-making toolkit to create a worm that, under the guise of an e-mail image of tennis star Anna Kournikova, spread like wildfire for two days in February 2001.
At the trial, De Wit stated that he did not know what he was doing or what the consequences of posting the virus in an Internet newsgroup could be.
The judges did not believe him because De Wit had an impressive collection of about 7,200 computer viruses and worked in a computer store. Damage done by the Kournikova worm was limited, but could have been significant. The court said that the rapid spread of the virus could have paralysed the Internet and that De Wit was aware of this.
News of the appeal comes shortly after the writer of the Melissa virus, David Smith, was sentenced to 20 months in prison in the US. The Melissa virus spread in 1999 and is said to have caused more than $80m (£55m) in damage.