The present disclosure provides a display panel, a display device, their manufacturing methods, and a substrate curving device. The method for manufacturing the display panel includes steps of: providing two substrates for forming the display panel; arranging the two substrates opposite to each other, curving the two substrates at a predetermined curvature, and directly dripping liquid crystals into a space between the two curved substrates, so as to make the liquid crystals to have a twist angle matching with the predetermined curvature of the two curved substrates; and after the dripping, arranging the two substrates opposite to each other to form a cell. According to the present disclosure, the liquid crystals are dripped into between the two curved substrates, the then the two curved substrates are arranged opposite to each other to form the display panel.