The incident took place on Tuesday afternoon. The girl was standing near her house when the accused lured the girl by offering her a 'frooti' and took her to a secluded place, police said.
The victim was found in the bushes adjacent to a road and was spotted by a passerby.
She was initially rushed to the Deen Dayal Upadhyay Hospital from where she was shifted to the Safdarjung Hospital. Her condition is stated to be stable, the police said.
The victim could not tell her address or her parents' name when a lady officer tried to ascertain these details, the police said.
The police searched the area where the victim was found and located her parents.
They identified the accused with the help of CCTV footage obtained from the area. The footage showed the accused with the girl on the day of the incident.
"The identification of the accused became easier as he was wearing the same t-shirt which he had been wearing on the day of the incident," a police officer said.
The accused, who was unemployed and lived in the same locality as that of the victim, was subsequently arrested, the police said, adding that he had confessed to his crime.
A case has been lodged and investigations are on to ascertain whether the accused was involved in similar crimes in the past, the officer said.
Chairperson of the Delhi Commission for Women, Swati Maliwal visited the hospital and met the victim.
"Met 6-year-old rape survivor in Hospital. Shell shocked! Each inch of her body has marks of brutality. Private parts completely destroyed! Last year I kept hunger strike for 10 days 4 death to child rapists but yet to be implemented even in Delhi. The system is responsible for this rape!" she tweeted.