Sir Alan has found wider fame in The Apprentice
Sir Alan Sugar has stepped down as chairman of Amstrad but insists that he is not retiring.
The entrepreneur and self-made multi-millionaire has become known as the boardroom chairman in BBC reality TV show The Apprentice.
Amstrad was sold to BSkyB in 2007 and the 61-year-old will now continue to be involved with his numerous other business interests.
Sir Alan said it was now the "right time" for him to step down.
His other businesses include Amshold, Amsprop, Amsair and Viglen computers.
"The past 40 years have seen Amstrad grow from a start-up business to the success story that it is today, which is credit to the talented and loyal team here."
"This is a move that has been planned for a while and it's the right time for me to step down from my role at Amstrad," he said.
Sir Alan has achieved a net worth of £830m, but most of his wealth now comes from his property portfolio, rather than business ventures.
He left school at the age of 16 and founded Amstrad at the age of 21.
The company was floated on the London Stock Exchange in 1980, then sold to BSkyB in July, in a deal worth £125m that earned him a £34.5m windfall.