A cooling device for a vehicle electronic control unit, ECU. The cooling device includes a casing for covering the ECU and having a heat absorbing face for absorbing heat from components of the ECU and a heat dissipating face for dissipating absorbed heat. A plurality of fans are mounted to the heat dissipating face and are arranged to direct airflow over respective regions of the heat dissipating face. The fans are independently controllable for being driven at different speeds to vary the cooling of the respective regions of the heat dissipating face.