A 50-year-old man working on a ride at Sydney's Royal Easter Show has been charged with committing an act of indecency towards a two-year-old girl on Monday.

Police allege the man, who was employed by the owner of the carnival ride, committed an act of indecency towards the girl while she was on the ride.

The man charged was operating one of the rides at the Royal Easter Show. Credit:Brook Mitchell

A police statement said the child's mother witnessed the alleged act of indecency. She contacted police and later alerted the Royal Agricultural Society of NSW, which runs the Royal Easter Show every year.

Following inquiries, the man was arrested at the showground on Tuesday night and taken to Auburn Police Station.