The invention relates to a photovoltaic panel cleaning device which comprises a clamping part, a cleaning part, a support part and a controller, wherein the clamping part comprises a clamping support frame and a clamping component mounted on the clamping support frame; a photovoltaic panel is clamped and fixed by a left clamping plate and a right clamping plate in the clamping component; the cleaning part comprises a cleaning support frame, a brush component mounted on the cleaning support frame and comprising a brush, a dust collection component comprising a dust collector, and a positioning component comprising a positioning sensor; the upper part of the support part is connected with the cleaning part; the lower end of the support part is hinged to a rotary table which can be rotated; the rotary table is arranged on a movable support platform; the controller is mounted above the support platform; and the cleaning device is controlled to work by the controller. Meanwhile, the invention further discloses a cleaning method of the photovoltaic panel cleaning device. Through application of the photovoltaic panel cleaning device and the cleaning method, single photovoltaic panels with different cleaning heights as well as large-scale photovoltaic panels can be cleaned; the photovoltaic panel cleaning device is safe and reliable in clamping, works stably and cannot damage the photovoltaic panels easily; and meanwhile the photovoltaic panel cleaning device improves the usage rate and saves the cost.