Derek Mackay has resigned after claims emerged that he had sent inappropriate messages to a schoolboy, according to the BBC.
"I take full responsibility for my actions. I have behaved foolishly and I am truly sorry,” Mackay said as quoted by the Evening Standard.
"I apologise unreservedly to the individual involved and his family. I spoke last night with the First Minister and tendered my resignation with immediate effect,” he added.
Earlier, the Sun published a series of messages allegedly sent to the boy by Mackay.
According to the newspaper, he contacted the teenager over a six-month period, and offered to take him to a rugby game and out to dinner.
The accusations appeared as Derek Mackay prepared to disclose the Scottish Government's budget for the next year.