Goretzka joined Schalke from Bochum in June last year and enjoyed a strong first season at the Veltins Arena.
The 19-year-old scored five goals in 32 appearances in 2013-14 and was rewarded with a place in Germany's 30-man provisional squad for the FIFA World Cup.
Joachim Low cut Goretzka from the squad prior to Germany's title-winning campaign, but that has not prevented officials at Bayern from linking him with a potential move to the Bundesliga champions.
Bayern assistant Hermann Gerland recently remarked that it was "inevitable" that a player of Goretzka's ability would end up at the Allianz Arena.
But Heldt has been quick to dismiss Gerland's comments and is adamant that Goretzka will be not be going anywhere.
"This remark just underlines once again that Gerland has a very good eye for talented young players," Heldt told Sport Bild.
"Leon has got the quality and potential to play for a top club in Europe, only we're planning his future here with us.
"He is not for sale at any price."
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