The Nikkei share average advanced 1.11% to 26,812.30, after rising as much as 2% to its highest level since June 13. The broader Topix gained 1.44% to 1,914.66.
Prime Minister Fumio Kishida’s Liberal Democratic Party and its junior partner Komeito won 76 of the 125 seats contested in the chamber, compared to 69 earlier, according to an exit poll by public broadcaster NHK.
The election was held two days after the assassination of former Prime Minister Shinzo Abe, a dominant politician and power broker.
“The market was boosted by expectations for a long-term stability of Japan’s political base,” said Maki Sawada, strategist at Nomura Securities.
“But cautions ahead of corporate earnings reports may cap gains of the Nikkei this week, and concerns over a rise in new COVID-19 cases could weigh on sentiment.”
Phone company KDDI rose 3.26% and was the biggest boost for the Nikkei. Uniqlo owner Fast Retailing gained 0.94%.
Automaker Toyota Motor and Sony Group boosted the Topix, rising 1.94% and 2.11%, respectively.
Bucking the trend, chip-making equipment maker Tokyo Electron weighed on the Nikkei, falling 1.38%, after Nomura Securities cut its rating to “neutral” from “buy”.
Its peer Advantest edged 0.27% lower.
Yaskawa Electric, a robot maker seen as a leading indicator on Japanese manufacturers’ earnings trend, fell 5.61%after its quarterly earnings missed market consensus.