It is reported by NHK with reference to the department.
According to the channel, the disease was detected in a resident of Tokyo.
No other details have been provided yet.
Earlier, the head of the World Health Organization, Tedros Adhanom Ghebreyesus, declared the outbreak of monkeypox a public health emergency.
On July 12, the first case of monkeypox was confirmed in Russia.
The disease was detected in a citizen who returned from a trip to Europe.