Graham Nield, of Dewsbury, had planned to ask Amanda Vickers, 48, to marry him before he proposed on Sunday, but kept losing his nerve.
But after finding out his ticket matched all six Lotto numbers, Graham popped the question.
The 55-year-old said: “I checked the numbers on my phone app. I have five lines and the first four had nothing but the last line had all six balls ticked.
“I just couldn’t believe it so I gave Amanda the phone. She checked the numbers on her iPad and started screaming and jumping up and down.
“I was caught up in the moment and just blurted out ‘now will you marry me’ and she said told me ‘yes, but it isn’t because you’ve loads of money it’s because I love you’.”
Graham had been planning on proposing to Amanda, who grew up in Chickenley, on a recent holiday to Tenerife.
He said: “Every morning for breakfast I got really nervous and in my head I kept telling myself to ask the question but it just would not come out.”
Despite picking up the six figure fortune, the couple both went to work at the Autoneum in Heckmondwike on Monday.
Graham, who bought the ticket from Tesco in Bradford Road, Batley, attended all his morning meetings before calling the lottery office.
The couple recently left their home in Hanging Heaton to move in with Amanda’s parents, James and Joan Vickers, both 72, in Dewsbury.
Before the move, the pair visited Amanda’s parents to tell them the news.
Graham sprung another surprise on his future in-laws asking for permission to marry their daughter and got down on one knee to propose.
Despite the winnings, the pair are planning to keep their wedding low key.
“We are planning on getting married in the register office and have a big party afterwards,” said Graham.
Amanda won’t be splashing the cash on a diamond ring, but instead will keep an eternity ring previously bought by her fiancée.
The couple intend to share their winnings with their five children from previous marriages and are considering opening a cafe.