A fan fastening device used to fix a chassis having a plurality of fans to a housing. The fan fastening device includes two locking element and two lever assembly. Each lever assembly includes a first end and a second end opposite to the first end. Each first end is slidably fixed to one of the locking element, each second end is rotatably fixed to the chassis and resists the housing; the locking elements are pulled away from the housing to drive the lever assemblys pulling the chassis until the chassis is detached from the housing.