The discovery came as construction workers prepared a road expansion project on Wednesday morning, police spokesperson Kiyotaka Maedomari said.
"Because unexploded bombs from World War II are scattered across Okinawa, construction workers always use metal detectors before starting to dig the ground," he said.
An army bomb disposal squad proceeded to discover a total of 902 bombs, believed to have been made in the United States.
"It's rare to find this may unexploded bombs at once," Maedomari said.
Unexploded bombs are periodically found across Japan, but cases of injury-causing detonation are rare.
An estimated 10,000 tonnes of unexploded munitions were left in Okinawa after the war, and just less than half remained by the time the United States military reestablished itself on the island in 1972.
It is expected to take 80 years or more to remove the bombs that remain.