The invention provides a display device which can reduce breaking of a TFT substrate at the time of connecting a wiring member to the TFT substrate after decreasing a thickness of the TFT substrate and a manufacturing method of the display device. A TFT substrate and a counter substrate are adhered to each other to form a display panel. After connecting a wiring member to a line connection portion of the display panel, a portion of the display panel to be etched is masked. An etching protective film formed of an organic film is applied to the masked display panel by coating. Thereafter, a mask is peeled off together with the etching protective film formed on the mask and the display panel is immersed in an etchant thus polishing an exposed surface of a glass substrate to a predetermined thickness. Thereafter, a chemical polishing protective film formed on a wiring member is removed.