Troy Bell, 51, was convicted last week of 20 counts of theft and six counts of dishonestly dealing with documents, committed between 2009 and 2013.
The independent member for Mount Gambier said it had been a tough time since the verdict and he'd taken time to consider his position.
"These past few days have been incredibly difficult for my family and myself as we come to terms with the jury's decision," he said in a statement on Tuesday.
"After reflection, I am now ready to make a public statement.Â
"Based on the legal advice I have received, I have instructed my legal team to proceed with filing an appeal."
Bell said he would not make further comment while the matter remained before the court for sentencing and the appeal.
The trial, which began in June, heard evidence that Bell abused his position as an Education Department employee to steal more than $430,000 meant to help vulnerable high school students and used it to fund property investments and pay debts.
Much of the trial focused on the movement of money between bank accounts and included five days of evidence from a forensic accountant.
During the trial, prosecutor Jemma Litster said there had been "backwards" transfers between Bell's personal accounts and the not-for-profits' accounts "but there was still $436,023 that went out that didn't come back".
Earlier on Tuesday the state Labor government said it would support a motion to have Bell's seat vacated and a by-election called, should he not lodge an appeal.
That course of action would still be likely should Bell fail to overturn his convictions.
Bell's case is scheduled to return to court on October 15 for a directions hearing ahead of a date being set for sentencing submissions.
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