Police said the woman, 44, identified only by the surname Law, was arrested at Hong Kong International Airport as she attempted to board a flight to Thailand.
The maid, Erwiana Sulistyaningsih, is hospitalized in Indonesia after alleged beatings by her employer, representatives from a migrant workers' union said. They said she has blurred vision and finds it difficult to eat or sit up without aid.
The Hong Kong government said police and labor officers will visit Sulistyaningsih Tuesday.
Photographs depicting her injuries have spurred anger in Hong Kong and a protest march of about 5,000 demonstrators took place Sunday in Hong Kong, the Wall Street Journal reported Monday.
Some 300,000 foreign domestic workers are employed in Hong Kong, many of them from Indonesia.