The attack happened late Monday at the Hirakawa Zoological Park in the southern city of Kagoshima.
At just past 5:00 p.m., an employee at the Hirakawa Zoo alerted emergency services after the tiger bit 40-year-old Akira Furusho.
A white tiger has mauled a zookeeper to death at a zoo in southern Japan. He was declared dead in hospital.
Zoo officials said they believe Furusho went inside the cage to clean the enclosure and was probably attacked while trying to move a male tiger to its night cage.
The zoo was scheduled to remove the tiger from display to his sleeping chamber at the time.
A police official told AFP: "A zookeeper was found collapsed in a cage, bleeding", confirming that he later died.
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The zoo was open as normal on Tuesday but the white tiger observation zone was restricted "as police continued to investigate the case", AFP reported.
Police said they are investigating whether proper safety measures were in place at the zoo.
The tiger was sedated with a tranquilliser gun.
No one saw the moment of the apparent attack.
White tigers, regarded as an endangered species, are found in southern and eastern Asia, particularly India, and owe their colour to a recessive gene.