An armed man sexually assaulted and robbed a 36-year-old woman behind a Queens apartment building last week, police said Monday.

The victim was walking near 70th Street and Roosevelt Avenue in Elmhurst when the brute, armed with a gun, approached her and forced her behind a nearby building at about 1:15 a.m. last Monday, cops said.

The sicko then sexually assaulted the woman before robbing her of $60 and her cell phone, police said.

He ran off after the attack and remained at large early Tuesday, police said.

The suspect is believed to be between 20 and 25 years old. He was last seen wearing a black jacket, light colored pants and black sneakers.