The Peep Show comedian's recreation of the iconic dance from the 1980s film Flashdance narrowly beat the Dirty Dancing efforts of Keith Lemon and Paddy McGuinness.
Last night's final brought to an end four weeks of heats and dance-offs held to raise funds for the charity.
Accepting the trophy, the BBC reports Webb as saying: "I feel fantastic. It's been marvellous, it's been like falling in love with myself all over again."
Head panellist Anton Du Beke said all the contestants had outdone themselves. "I wish we could have a big old tie, personally," he said.