Whenever someone logs into Facebook, Facebook records that person's IP address. While Facebook can divulge someone's IP address to law enforcement authorities, the company doesn't make this information available to anyone else. However, there's a way to find someone's IP address if you're chatting with that person in Facebook or any other instant messaging platform.
Facebook can provide law enforcement authorities with recent IP addresses and other information about an account if it's needed in a criminal investigation, such as through a court order or subpoena. Facebook may also opt to give this information to law enforcement if the company believes the information is required to prevent illegal activities. If you're reporting a crime involving Facebook, the police may be able to get location information about an account using its IP address.
Finding an IP Address Yourself
It may be possible to discover someone's IP address by initiating a Facebook chat session with him. First close all other tabs in the browser. Once the person responds to you in a chat session, type "Cmd" (without quotes here and in subsequent commands) in the Search charm in Windows and press "Enter" to launch the Command Prompt app. If you type "netstat -an" in the command prompt window, the person's IP address should be listed along with all the other IP addresses your computer is communicating with.