Joseph Edward Auton appealed against his sentence of three and a half years' jail on the grounds it was manifestly excessive and argued his sentence did not take into account his guilty plea or medical factors.

The Court of Criminal Appeal agreed the sentencing judge Justice Robert Pearce was correct in his original sentencing of the appellant due to the nature of the criminal offence.

Auton repeatedly ill-treated a three-and-a-half-year-old child with severe Autism Spectrum Disorder between August 12 and September 2, 2016.

Auton met the victim's mother in June 2016 and a month later the victim's mother and the victim moved to a rural property where Auton was living.

Over a three-week period, the victim suffered from bruises, lacerations, scratches and abrasions to his head, face, arms, legs, upper and lower torso as the result of force applied to the child by Auton.

In her reasons, Justice Helen Wood said Auton's sentence must reflect the serious nature of ill-treating a child.

"The ill-treatment occurred repeatedly over a prolonged period where the appellant had plenty of time to reflect on what he was doing when the consequences of his actions, and the child's distress, would have been obvious," Justice Wood said.

"The suffering caused to the child was considerable and inevitable given the nature of the ill-treatment."

Auton will be eligible for parole after serving two years' jail.