The injured inmate was admitted to a hospital, Jail Superintendent Rakesh Mohan Sharma said adding the attackers included the accused in the Bhanwari Devi abduction and murder case.
Undertrial Anil alias Pandia, hailing from Sikar, was beaten up by 13 prisoners during the distribution of meals in the morning following an argument, Sharma said.
The prison staff intervened immediately and separated them, the Jail Superintendent said.
"We have admitted him in the hospital and informed the police," he said.
This is the second clash among the prisoners in a month. Inmate Vicky was attacked by other prisoners on April 20.