According to the prosecution, Gupta had abducted the school girl, raped her and murdered her to destroy evidence in December 2009.
The accused, who was married and has two children, worked as a contract labour with a company in Thane city.
The victim's father, a resident of Lokmanya Nagar, told the court that on December 24, 2009, when he returned home in the evening from work, he was told that his daughter, a Class II student at Saint Ulai School, had not returned till then.
When he went out in search of her, Gupta met him on the way and told him that he had met the girl and gave her chocolate and biscuits.
The parents lodged a missing complaint with police and the next day her body was found under a hillock.
Additional Public Prosecutor Hemlata Deshmukh said this was a rarest of the rare case which deserved nothing less than death sentence.
The court, relying on the witnesses from the vicinity and circumstantial evidence, held that the accused was guilty of the charges levelled against him and sentenced him to death.