Richard Smith, from Kanawha County, West Virginia in the United States, was convicted of 11 counts of first-degree sexual abuse, four counts of first-degree sexual assault and five counts of sexual abuse by a parent or guardian, according to abc15.
Due to be sentenced on March 4, he faces 205 to 775 years in prison.
The baby's grandma, and Smith's alleged accomplice, Roseanna Thompson, 46, will stand trial on the same charges, along with a count of incest in March.
The alleged crimes took place in 2015 at a home in South Charleston.
According to WCHS, the abuse was uncovered when Smith's ex-wife Morgan Smith discovered the video tapes of the pair allegedly abusing the little girl.
'Just completely blew me away, turned my entire world upside down,' she said.
'It baffles me because I think kids are to be protected and cherished at all costs, so to know that somebody that I loved could do this...'