An exemplary fan duct includes a top plate, two sidewalls and a baffle. The sidewalls extend from opposite ends of the top plate. The baffle engages with the top plate and is located between the two sidewalls. The baffle includes a first end and a second end opposite to the first end, the first end pivotably engages with the top plate, and the baffle rotates about the first end to make the second end engage with the top plate or one of the sidewalls.