A health department official says the 29-year-old man arrived from Dalian in northeast China late on Tuesday and later complained of a high temperature - one of the symptoms of Severe Acute Respiratory Syndrome (SARS).
The tourist was transferred to Queen Elizabeth hospital early on Wednesday to undergo a variety of tests, including chest x-rays and blood samples, as a precaution. But the tests have proved to be negative.
It's not immediately known what illness the Japanese man has.
SARS killed 299 people in Hong Kong and infected nearly 1800 others between March and June, making Hong Kong the world's worst affected region after mainland China.
The SARS outbreak had a serious impact on business and tourism in southeast Asia. Hotels and restaurants stood empty during the pandemic as business people and tourists cancelled visits to the region.