The 56-year-old employee of a Kasai Municipal Government-run waste disposal center found the bag while separating garbage for the disposal.
Center officials handed the bag into the police and will be entitled to claim the cash if its rightful owner does not emerge within three months.
“You hear about these things on the news sometimes, but it’s a shock when it happens to you,” Kasai Mayor Kazuhira Nishimura said. “We hope it quickly gets back to its rightful owner.”
Police said the bag was stuffed with mostly 10,000 yen notes. Most of the notes had been made from at least 2004 onwards as they contained a hologram in the lower left-hand corner. Police will ask the Bank of Japan to examine the cash.