A team of Shahbagh Police arrested the couple and rescued the victim from the house on Saturday night.
The domestic help, identified as Sweety, hailed from Mithamoin upazila of Kishoreganj district. She has been working there for nine months, said police.
The couple used to torture the girl over trifling matter, said police quoting the victim.
A neighbour posted the image of the victim with several injury marks, on social media on Saturday night and sought help and legal action.
A journalist found the post and sent it to the Media and Public Relations Wing of Bangladesh Police and sought action.
Police took action after one and half hours of the Facebook post.