The man, identified only as Denis, from the village of Gnilushi, in south-west Russia's Lipetsk region, is said to only have stopped beating the disabled toddler once she started bleeding heavily.
Doctors said she died from massive internal injuries and blood loss.
A police spokesman said:
"The autopsy results said the girl died from internal bleeding caused by the fracture of internal organs. Denis has admitted his guilt. He has been detained."The girl was adopted by Denis and his wife from an orphanage. The couple already have four children of their own.
Authorities said the injuries sustained by the little girl were so severe that it might not have been the first time she was assaulted.
Meanwhile the couple's four children have been taken into care while Denis awaits trial in prison.
Source - TheSunUk