The invention relates to a thin diaphragm battery. The battery comprises a positive electrode plate, a diaphragm and a negative electrode plate which are successively laminated. The positive electrode tab is led out from one end of the positive electrode plate. The negative electrode tab is led out from one end of the negative electrode plate. The positive electrode tab and the negative electrode tab are arranged on the same side of a battery body. The thin diaphragm battery also comprises a first outer packaging diaphragm arranged on the positive electrode plate side and a second outer packaging diaphragm arranged on the negative electrode plate side. The first and second outer packaging diaphragms are sealed peripherally for packaging the positive electrode plate, the diaphragm, the negative electrode plate and electrolyte of the battery. The positive electrode plate comprises a current collector layer and a positive electrode material layer with which the current collector layer is coated. On one side of the first outer package diaphragm, close to the positive electrode tab, extends outwards to form an extension sheet. One surface of the extension sheet, facing to the positive electrode tab, is coated with sealant. The positive electrode tab and the negative electrode tab are fixedly stuck on the extension sheet of the first outer packaging diaphragm. The thickness of the battery is 0.1-5.5mm. The thin diaphragm battery disclosed by the invention has the characteristics of being thin, good in conductivity, good in tightness, and the like and the electrode tabs are not easy to break.