Martin Hackett, 26, grabbed the schoolgirl by the hair from behind on Craigton Road, Glasgow, before repeatedly hitting her with the weapon in broad daylight.
When passers-by heard the youngster screaming and went to her aid, Hackett ran off to his home just minutes away from the scene.
The child was bleeding heavily and suffered cuts and bruises including a gash on her forehead that needed stitches and has been left with a scar.
Yesterday at Glasgow Sheriff Court Hackett was found guilty of assaulting the now 10-year-old to her severe injury, permanent disfigurement and danger of life, on June 22, 2012.
He was also found guilty of behaving in a threatening or abusive manner on August 24, 2012, at a flat in Glasgow, but the jury returned a not proven verdict to a charge of assault on his ex- girlfriend Zoe Francis.
Hackett pled not guilty and had lodged a special defence of alibi on the first charge, claiming he was at home when the child was attacked.
Sheriff Kenneth Mitchell deferred sentence on Hackett until next month for reports.