The invention discloses an oil tank body shaping machine, which comprises a frame, a lower shaping frame horizontally arranged on one side of the frame, at least one oil cylinder which is vertically arranged on the lower shaping frame and of which the piston rod extends upwards, and an upper shaping frame horizontally arranged at the upper end of the piston rod. The upper shaping frame and the lower shaping frame are symmetrically arranged; and an arc-shaped chamfer is formed on each side of the upper shaping frame and the lower shaping frame in the width direction. Two oil cylinders are symmetrically arranged; the upper shaping frame is arranged at the upper ends of two piston rods through two hinge bases; the upper end of each hinge base is fixedly connected with the upper shaping frameand the lower end of each hinge base is hinged with the upper end of a corresponding piston rod through a pin shaft; two groups of mutually symmetrical guide pieces are arranged between the lower shaping frame and the upper shaping frame; each group of guide pieces consist of a lower guide post and an upper conduit which are sleeved internally and externally and are vertically arranged; the lowerend of the lower guide post is fixedly connected with the lower shaping frame; and the upper end of the upper conduit is fixedly connected with the upper shaping frame. The oil tank body shaping machine can conveniently shape the arc-shaped chamfer of an oil tank body, and has better shaping effect and higher efficiency.