Edinburgh Sheriff Court heard Mark Gallacher, 27, of Northfield Park, started a relationship with the teenager after she accidentally called his mobile phone in July, 2005.
He returned the call and they began to contact each other every day. She pretended to be an 18-year-old college student at first but later admitted she was just 14.
They met for the first time in January this year. It was then that she admitted her age, but Gallacher continued to see her. Two months later he had sex with her.
She admitted to her father that she was seeing the older man but claimed that it was an innocent relationship.
Her furious dad told her to put an end to the affair and began to check her text messages. But it continued.
Sheriff Charles Stoddart ordered Gallacher to register as a sex offender and told him to return next month for sentence.