A negative electrode material contains an organic anti-shrink agent which is soluble in water, and the organic anti-shrink agent, when extracted from the negative electrode material with an alkali aqueous solution, has an average particle size of not less than 0.1 μm and not more than 9 μm in sulfuric acid having a specific gravity of 1.25. A lead-acid battery includes a negative electrode plate containing an organic anti-shrink agent having a S element content of 4000 μmol/g or more. The negative electrode contains 0.3 mg/cm3 or more of the S element in the organic anti-shrink agent.