A sicko forced his way into a Brooklyn woman’s apartment and raped her at gunpoint, cops said Saturday.

The suspect knocked on the victim’s apartment door at 52nd Street and 7th Avenue in Sunset Park around 1 a.m. Friday, police said, then forced his way inside when she answered.

The attacker pushed the 34-year-old woman into her bedroom, pulled a handgun, and raped her, police said.

When he demanded cash, the woman handed over $500, police said.

He used a sweater to tie her arms, and ran. The woman was able to free herself and called 911, cops said.

Police say the suspect is in his 30s and around 5-foot-8 with a medium build.

Surveillance video shows him talking on the phone and smoking a cigarette in the area before the incident.