Fritzl, 73, had earlier denied charges of murder and enslavement, but had pleaded guilty to rape, incest, and false imprisonment.
When the judge asked why he had changed his plea to guilty on the last two counts, Fritzl cited the 11 hours of videotapes of his daughter's testimony that were shown in court.
Fritzl locked Elisabeth in a soundproof basement at the family home shortly after she turned 18. Over the next 24 years, Fritzl used her as his sex slave, raping her over 3,000 times. He also fathered seven children with her.
Three of the children were adopted by Fritzl, while three remained in the basement.
Fritzl is accused of murdering the seventh child, a boy, who died shortly after birth in the basement, and received no medical treatment. He burned the body in an incinerator shortly after its birth. An eighth child miscarried.
The shocking case came to light in April last year when one of the children Fritzl fathered with Elisabeth was taken to a hospital with a serious medical condition. Kerstin, 19, has since recovered and is living with her mother and five siblings at an undisclosed location.
Fritzl's wife, Rosemarie, said she knew nothing about what went on in the basement. She believed her daughter had joined a religious cult, and had left the three children on the doorstep because she could not take care of them.
The Fritzls' home in Amstetten was bulldozed by the authorities back in November.
