The five-year girl was abducted April 15 and kept hostage by her neighbour for two days without food and water and repeatedly raped in east Delhi's Gandhi Nagar, police said.
Accused Manoj Kumar, 25, was arrested from a village in Bihar's Muzaffarpur district early Saturday, police said.
The girl, rescued Wednesday, is undergoing treatment in All India Institute of Medical Sciences (AIIMS).
According to police records, a two-and-half year girl was raped by a 25-year-old man in west Delhi's Najafgarh April 18. Accused Rajdhir has been arrested.
Another five-year girl, studying in lower kindergarten, was sodomised by her teacher in the school premises in east Delhi's Jagatpuri area April 17. Accused Pramod, 32, was arrested, police said.
A 15-year Class 10 student was also gang-raped April 17 in east Delhi. One of the accused was related to her, police said.
Three accused abducted the Class 10 girl from New Ashok Nagar area while she was on her way to school and gang-raped. One of the accused, Pradeep, 28, has been arrested. Co-accused Rahul and Amit are absconding, police said.
In west Delhi's Sultanpuri area, a 10-year girl playing outside her home was lured away by neighbour Rakesh Kaushal into a stationary bus and raped in April 14. Kaushal was arrested, police said.
Delhi police spokesperson Rajan Bhagat told IANS: "A total of 393 cases of rape have been reported between Jan 1 and March 31."
From Jan 1, 2012 to Dec 15, 2012, a total of 661 rapes were reported in the capital, according to police records.