Chuanfang Zheng had been trusted to babysit seven-month-old Phoebe Guo at a flat in Lutterworth, Leicestershire, on 22 March 2015.
The baby became unconsciousness and died four days later.
Zheng, 31, of Mortlock Close, Southwark, London, will be sentenced on 24 February.
The judge warned her she could expect a long prison sentence.
Det Ch Insp Natalee Wignall, who led the investigation, said that while the conviction "would not bring Phoebe back", justice had been done.
Leicester Crown Court was told Phoebe suffered "significant bleeding" on the brain and behind the eye within half an hour of being left with Zheng.
Adrian Langdale, prosecuting, said it would never be possible to establish exactly what happened behind closed doors that evening.
"Chuanfang Zheng must have caused significant abusive head trauma described historically as 'shaken baby' and described by an expert as being 'very much at the severe end of the range'," he said.
"It would have been immediately apparent to Chuanfang Zheng what she had done."
With the unconscious baby in her arms, Zheng ran to a Chinese takeaway next door on Linden Drive where the baby's parents worked.
Phoebe was then rushed by car to hospital and there were '"extensive" medical efforts to save her, the court heard.
However, she died four days later from her severe injuries, having never regained consciousness.
The jury was told Zheng made a concerted effort to lie about the events leading up to the incident and had tried to cover up her actions.
Zheng also tried to blame the mother's efforts to resuscitate the baby for causing the serious injuries.
Commenting on the case, the NSPCC warned that "just a moment's loss of control" can result in a tragedy.
An NSPCC spokesman said: "There is no excuse for a carer to inflict such appalling injuries no matter what pressure they might be experiencing."
An aunt who "repeatedly, vigorously and aggressively" shook her baby niece has been found guilty of the girl's manslaughter.