The present invention is directed to a binder for electrode materials which comprises tetrafluoroethylene polymer fine particles having an average particle size of not more than about 0.20 .mu.m and having a standard specific gravity of not more than about 2.20, wherein a mixture prepared from said fine particles with about 17% by weight of the total mixture of an extrusion coagent, when subjected to the measurement of an extrusion pressure by a rheometer, exhibits under the conditions of a draw ratio of 100 to 1 and an extrusion speed of 18.+-.2 mm/min, an extrusion pressure of not less than about 220 kg/cm.sup.2.