To suppress the corrosion rate at a grating and to provide a lead-acid battery with excellent life properties by injecting a molten metal of a lead-tin- calcium alloy including calcium of a specific ratio into a mold, and by cooling at a specific rate to solidify the molten metal.

In this manufacturing method, it is preferable that a molten metal of a lead-tin-calcium alloy including calcium of 0.01 to 0.06 wt.% is injected into a mold and is cooled at a cooling rate of 27 deg/sec. or under for solidification. Grating-like engraving is applied to a pair of a molding material consisted of Meehanite cast iron buried with a cooling pipe, a lubricant is sprayed and a metal mold of a grating provided with a thermal barrier of 100 μm is attained. The temperature of the metal mold is maintained at 150°C and the lead-tin-calcium alloy is injected and cooled. When calcium is 0.01 wt.%, the cooling rate is 23 deg/sec. and the grain boundary corrosion rate is 0.15 (mm/mm2); and when the cooling rate is 33 deg/sec., the grain boundary corrosion rate is 0.40 (mm/mm2). When calcium is 0.06 wt.%, the cooling rate is 23 deg/sec. and the grain boundary corrosion rate is 0.06 (mm/mm2); and when the cooling rate is 33 deg/sec. and the grain boundary corrosion rate is 0.28 (mm/mm2).