The Lionesses, who had already qualified for the last 16 and needed to avoid defeat to win the group, went ahead just before the quarter-hour mark through White’s cool finish following good work by Georgia Stanway.
White then slotted in her second, and third of the tournament, with six minutes of normal time remaining having been teed up by substitute Karen Carney.
Japan goalkeeper Ayaka Yamashita made a number of fine saves during the contest at the Allianz Riviera, after her counterpart Karen Bardsley had done well to tip a Kumi Yokoyama free-kick onto the bar in ninth minute.
“We expected Japan to come at us hard in that second half so we were ready for it,” said White.
“We did well and we stuck together and we got the win. It’s three wins from three so we take a lot of momentum into the knockouts now.
“I love scoring against Japan and playing for my country – it’s a dream to be here. We’ll keep growing as the tournament goes on. Our objective was to win the group and we’ve done that. Now, we need to recover and get ready for the next game.”
Phil Neville’s England will now face a third-placed finisher in the next round – either China (Group B), or Cameroon or New Zealand (Group E), or Chile or Thailand (Group F) – on Sunday in Valenciennes.
Scotland crashed out of the World Cup in heart-breaking fashion after letting slip a three-goal lead to draw 3-3 with Argentina.
Shelley Kerr’s side appeared on course for the win they needed in their final group game as goals from Kim Little, Jennifer Beattie and Erin Cuthbert put them 3-0 up with 21 minutes remaining at the Parc des Princes.
Qualification for the knockout stage was within Scotland’s grasp as one of the best third-placed finishers.
But Argentina hit back through goals from substitute Milagros Menendez and Florencia Bonsegundo, who then scored a retaken penalty in stoppage time after her initial spot-kick had been saved to send the Scots home.