Japan built a 12-0 lead by the sixth inning, when the Netherlands closed on Wladimir Balentine's three-run double and Andruw Jones' RBI single.
Hayato Sakamoto's grand slam in the seventh that made it 16-4 and tied the team record of six homers, set by Cuba against South Africa in 2009. The game was called under the 10-run mercy rule when the Netherlands failed to close the gap in the bottom half.
"We've achieved our first goal of advancing to the final round," Japan manager Koji Yamamoto said.
Takashi Toritani homered leading off the game, the first home run for Japan in five games at 16-nation tournament.
Nobuhiro Matsuda widened the lead to 3-0 with a two-run homer in the second, and Seiichi Uchikawa made it 6-0 with a three-run drive that chased Rob Cordemans, who allowed six runs and five hits in 1 1-3 innings.
Atsunori Inaba hit a solo homer in the third against Tom Stuifbergen, and Yoshio Itoi had a three-run homer in the fourth. Sakamoto's slam came off Berry Van Driel.
Japan outhit the Dutch 17-6.
Japan scored 17 runs in its first four games of the tournament and wasn't expected to rely on the long ball. Yamamoto's team has no players from the American major leagues.
Kenta Maeda allowed one hit in five innings, struck out nine and walked one.
"My fastball and offspeed pitches were working well today," Maeda said. "I knew it was a big game, so just tried to stay calm and pitch in my usual way. We're happy to be going to the United States."