A fan cage is at least adapted to a first fan and a second fan smaller than the first fan. The fan cage includes a cage body and an adjustment member. The cage body defines a first accommodation portion in a size fitting the first fan. The adjustment member is movably disposed on the cage body and switchable between a laid down status and an upright status within the first accommodation portion. When the adjustment member is in the upright status, the adjustment member is upright in the first accommodation portion so that the adjustment member and the cage body together define part of the first accommodation portion as a second accommodation portion in a size fitting the second fan.