I believe both of you are great and thank you both for your answer.
But which one shall I trust?
I'm trying to use it in China, which has the volatage of 220V 50Hz, do you think it is possible?
From the specification page provided at Japan site:http://buffalo.jp/products/catalog/item/h/hs-dhgl/index.html?p=spec
I can see it says
AC100V 50/60Hz , so it doesn't look a typo.
So it looks like ScottP is right.
BTW: is there some component that I can add thus I don't need the extra transformer outside? Thanks.