The new cases bring the total of infected patients on the Diamond Princess to 61, with around 3,700 passengers and crew being held in quarantine in the port of Yokohama.
Japan's Health Ministry confirmed the news as China announced that the death toll from the flu-like disease had risen to 633.
That means 73 new deaths in one day, the highest daily death toll since coronavirus was first detected.
The Chinese National Health Commission findings show this is the second day in a row that record death tolls have been recorded.
On Thursday, a record 70 died from coronavirus in Hubei province alone.
All of the Diamond Princess' passengers and crew have been put on lockdown since Monday night when the ship arrived at Yokohama after an 80-year-old man from Hong Kong who disembarked last month tested positive for the virus.
The ship had been on a 14-day trip to Southeast Asia.
Princess Cruises, the company which owns the Diamond Princess, has cancelled two other planned cruises on the ship departing from Yokohama this month.
In Japan, fears are growing in places where the Diamond Princess made port calls before returning to Yokohama.
Health officials in Naha, capital of Okinawa Prefecture, said 13 people had left the ship there on Saturday and not returned.
Some of the missing passengers have since left the country.
The 2,600 passengers who got off for at least a few hours in Naha on Saturday "did not display symptoms at the quarantine screen station," local health official Takahir Hayamizu said.
"We don't have detailed information on who they were, so we cannot track down their route in Okinawa."
Passengers onboard the quarantined ship have spoken of the grim life on the ship.
One passenger wrote on Twitter: "I keep hearing painful coughs from a foreigner in a nearby room."
Noting with alarm that crew members were delivering meals door to door, he warned: "I might get infected today or tomorrow."
The total number of coronavirus cases worldwide stands at 31,481 so far, of which 4,824, or roughly 15%, are in a critical condition.
So far, 638 people have died worldwide from the disease, the vast majority in China's Hubei province, where the virus was first detected at a food market in the region's largest city Wuhan.
Only two deaths from the disease have been recorded outside of mainland China, one in Hong Kong and one in the Philippines.
There have been three confirmed cases in the UK, two in Yorkshire and one in London.
On Thursday, a baby was taken to hospital in Derry, Northern Ireland for coronavirus testing after becoming sick following a flight from Hong Kong to Belfast last week.