A pet cage door including a door frame and a door capable of opening and closing relative to the door frame. A locking device is disposed between the door and the door frame and includes a housing disposed on the door. A horizontal locking tongue which is horizontally movable to insert into a horizontal socket in the door frame is disposed in the housing, and a vertical locking bar which is vertically movable to insert into a vertical socket in the door frame is also disposed in the housing. The housing is also provided with a drive mechanism which is matched with the horizontal locking tongue and drives the vertical locking bar to unlock while driving the horizontal locking tongue to unlock.
