Bol's time beat the previous record of 49.59 set by Czech athlete Jarmila Kratochvilova on March 7, 1982.
"It was because of all the fans here that I ran this record," said the 22-year-old, who claimed bronze in the 400m hurdles at the Tokyo Olympics behind Americans Sydney McLaughlin and Dalilah Muhammad.
"Never have I ever seen that many people here. When I crossed the line I knew that the record was mine because of the noise that the crowd made."
The outdoor 400m world record is 47.60, which was set by German Marita Koch in 1985.