Chikage Ogi, minister of land, infrastructure and transport, will be hospitalized for a week due to a liver complaint, ministry officials said Friday.
The officials said Ogi, who heads the New Conservative Party, had a fever Thursday and was hospitalized the same day.
Her illness apparently stems from the strain of dealing with the aftermath of Tuesday's terrorist attacks in the United States.
Ogi was absent from a Cabinet meeting Friday morning, but party officials said it is possible that she will take part in other meetings from the hospital.