An apparatus for a lighting device with a rotatable support includes a lamp body, the lamp body is provided with the support capable of rotating relative to the lamp body, the support is provided with a magnetic block, and a lighting port of the lamp body is arranged on the side wall of the lamp body toward the direction of the rotation center line of the support. When the adjustable lighting device is used, the support is fixed on a metal object in a place to be illuminated through the magnetic block and the side face direction of the lighting port of the lamp body can be adjusted by adjusting the lamp body to rotate relative to the support, and therefore the side face lighting angle of the lighting port is adjusted, and due to the fact that the lamp body can rotate relative to the support at any angle, stepless adjustment of the side lighting angle of the lighting port can be achieved.