Disclosed is a variable spoiler apparatus of the rear bumper for vehicles. The variable spoiler apparatus includes a linkage device, to be installed on a bumper back beam, which is able to vary in length in an up-down direction during a rotating operation. A spoiler is coupled to the linkage device and is able to move in the up-down direction by the rotation operation of the linkage device. A first drive device, to be installed on the bumper back beam, includes a first rotating shaft coupled to the linkage device to transmit a rotating force. When the first drive device is operated, the linkage device is rotated by a rotation of the first rotating shaft so that the spoiler is moved in the up-down direction. A second rotating shaft is rotatably coupled to the linkage device. The second rotating shaft is penetrated and connected to a second drive device.