An enclosed lead battery-use separator comprising fine glass fibers (1) as a main component, inorganic powder (3), beaten natural pulp (2) and heat fusing organic fibers (4). The heat fusing organic fibers (4) each have a size of up to 1.5 d (denier) and a fiber length of at least 1 mm, and is contained in an amount of 3-15 wt.%. The separator is excellent in short-circuiting resistance between the anode plate and the cathode plate of a battery including electrochemical and mechanical short-circuitings such as lead infiltration short-circuiting, excellent in bending strength, resistance against repeated bending and tear strength, easily formed into a bag-like separator, and free from a problem of an active matter coming off from a side portion. This separator improves the output, capacity, stability and life of an enclosed lead battery.