The health ministry also reported three new deaths, raising the death toll to 1,009.
Of Saturday's new cases, 295 were in the capital Tokyo, which has now seen five consecutive days of more than 200 infections.
Case numbers have been rising in Japan in recent weeks. On Friday, the health ministry reported 981 new cases -- the highest single-day toll since the pandemic began.
The virus has also spread through US military bases in Okinawa prefecture, with 229 infections linked to the bases.