The invention discloses an automatic welding device of a curved plate, comprising a roller base, a rotary assembly jig, a drive unit, a welding trolley and a control system, wherein, the roller base is composed of a base, four axle bases, a support roller and a sprocket wheel, the axle bases are arranged on four corners of the base, and the support roller and the sprocket wheel are axially arranged on a support shaft; the rotary assembly jig is composed of a welding platform and circular arc tracks, wherein, the two circular arc tracks are arranged on the bottom of the welding platform in parallel, and a roller chain is arranged along the circular arc tracks; the drive unit is composed of a servo motor, a reduction box and a transmission shaft, wherein, the reduction box drives the sprocket wheel by the transmission shaft; the welding trolley is arranged on the curved plate; the control system is composed of a monitoring tracker and a programmable controller; and the welding platform is tangent to the outer diameter of the support roller of the base by the two circular arc tracks, and the sprocket wheel is meshed with the roller chain. The automatic welding device can ensure that a bent segmented welding line still keeps in a horizontal status in the welding process to automatically weld the curved panel, obviously improve the welding quality of a boat deck and effectively improve the production efficiency of shipbuilding industry.