The wooden door was on the house at 20 Forthlin Road, Allerton, Liverpool, when the Beatle legend lived there from 1955 to 1964.
It was bought at Dominic Winter Auctions, based in Cirencester, by a telephone bidder from Chorley in Lancashire, reported BBC online.
The house is now a National Trust property which is open to the public. The house was listed as a Grade II building by English Heritage last year.
Several Beatles songs are believed to have been composed there, including Love Me Do, I Saw Her Standing There and When I'm Sixty-Four.
South, a local musician, heard about the door, and collected it from the house. He kept it behind his sofa at his home in Lancashire.
McCartney's bedroom door from the same house sold at a London auction in 1995 for 2,875 pounds.