The 'Someone Like You' singer has been hotly tipped to appear at the event in 2013, but organiser Michael Eavis says he can't convince her because she gets daunted by the number of people who attend the event, held in Somerset, Southern England.
Speaking at The Ivor Novello Awards, Michael Eavis told BANG showbiz: ''Adele knows that we want her anyway, but she doesn't want to do anything outside.
''She comes every year usually and has her own little party, but going on the pyramid stage is a bit daunting, playing in front on 80,000 people, it's a bit much.''
Glastonbury is taking a year off to let its fields lie fallow, but when it returns next year, Michael said he's likely to invite Ed Sheeran - who has already performed at the festival a few times and took home Best Song Musically and Lyrically at the awards show - back.
Michael also said he was sorry heavy metal festival Sonisphere had been cancelled, but feels they misjudged their line up, which was set to see Queen and Adam Lambert, KISS and Faith No More headline.
He added: ''Sonisphere, are you surprised? I don't' think the line up was very strong was it? I mean Queen without Freddie. We'd never book Queen without Freddie.''
Tickets for Glastonbury 2013 will go on sale on October 4th.