Speaking ahead of a trip to the town's Corus steelworks, Mr Miliband told the Scunthorpe Telegraph that he could reverse Labour's drubbing at the May General Election.
In North Lincolnshire the party lost two long-standing MPs in Ian Cawsey and Shona McIsaac, while Nic Dakin held on to the Scunthorpe constituency but saw a large swing to the Conservatives.
While some blamed the expenses scandal engulfing former town MP Elliot Morley for Labour's performance, Mr Miliband said: "Shona and Ian worked their socks off in those seats, they were victims of a national swing, nothing else. I think we have to say this leadership election must be as focused on the 180 seats we've lost since 1997 as the 260 seats we've got.
"I've been going to seats we don't hold as well as seats we do for that reason, because we need to elect a leader who can get us back into the game.
"Part of the reason for the trip to Scunthorpe is to listen to people who didn't vote for us as well as people who did."
Mr Miliband is facing brother Ed, former ministers Ed Balls and Andy Burnham, and left-winger Diane Abbot in the race to succeed Gordon Brown as party leader. He has been the front-runner since the start of the contest, which ends with voting in September.
The winner must secure the backing of a combination of grassroots members, trade union members and MPs.
Mr Miliband, who was formerly foreign secretary, will travel from Scunthorpe to Hull for a hustings tonight.
He said: "We've got to understand why we got a kicking; because that's the first step to persuading people you're serious about not getting a kicking next time."
Promising a greater focus on housing and transport if elected, he added: "The reason we lost in 2010 is because the weaknesses of new Labour were addressed and the strengths were thrown away."
Yesterday Ed Miliband won the support of a second trade union in a week in his bid to become leader. He now has the support of two unions, as does his brother David.
Scunthorpe MP Mr Dakin nominated former health secretary Andy Burnham for the contest, but said he has yet to decide who to vote for.
Speaking to the Scunthorpe Telegraph earlier this month, Mr Burnham said that he could revive the party's fortunes in North Lincolnshire because he would be a "leader people can relate to and identify with".