Two goals from Ross Stewart put the hosts in control in the first half while Callum Doyle added a third five minutes before half-time.
Stewart then completed his hat-trick after the break before substitute Benji Kimpioka added a fifth with a neat finish.
Sunderland are now two points ahead of second-place Rotherham, although the Millers have a game in hand.
Our chief SAFC writer Phil Smith has delivered his verdict on how each player fared for Lee Johnson’s side:
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1. Thorben Hoffmann - 7
Virtually a complete bystander in the second half but made some good stops at key times in the first, and so more than played his part in this win. 7 Photo: JPI Media
2. Bailey Wright - 8
Defended really resolutely early on and never gave an inch. Then got involved with some fine attacking play in the second, including a fine assist for Stewart’s third. 8 Photo: JPI Media
3. Tom Flanagan - 9
One of his best performances of the season and indeed in a Sunderland shirt. The Black Cats scored five but the win was built on the way they initially subdued the physical forward line that Darren Moore selected. Flanagan was superb. 9 Photo: JPI Media
4. Callum Doyle - 7
A lovely moment as he scored his first Sunderland goal to all but settle the game before half time. Looked very comfortable defensively and in stepping out with the ball. 7 Photo: Frank Reid