The Office of the Head of the Department of Magical Law Enforcement is an office located at the Headquarters of the Ministry of Magic. Yaxley is the only known Head of the Department of Magical Law Enforcement who made use of this office, but presumably other Heads like Justus Pilliwickle, Bartemius Crouch, Amelia Bones and Pius Thicknesse used it, too.
Under Amelia Bones
While the office was still occupied by Amelia Bones, it was supposed to be where Harry Potter's disciplinary hearing take place in the summer of 1995 for underage magic. Cornelius Fudge changed it to Courtroom Ten at a different time in the failed hope that Harry would miss it.
When Yaxley became the Head of the Department of Magical Law Enforcement during the Voldemort/Pius Thicknesse regime at the Ministry, the office became his with the position. When Harry Potter, Ron Weasley, and Hermione Granger infiltrated the Ministry in 1997, Ron, who was impersonating Reg Cattermole of the Magical Maintenance Department, had to go to Yaxley's office because it was raining. Hermione suggested that he try to use Finite Incantatem to remove any hexes or curses that had been placed on the room. Ron, impersonating Reginald, asked if Yaxley had tried an umbrella, trying to be funny, which only infuriated him even further. Yaxley threatened Ron to have the office dried out in one hour, or his wife would be facing graver charges.