To provide a battery electrolyte quantity management device capable of finding weight of a charged electrolyte with high precision and determining whether the quantity of the charged electrolyte is proper or not.

A weight m0 of a battery can, into which a wound group is inserted, is measured by a first weight measurement device 41, and then, after charging the electrolyte and installing a sealing body, its weight m is measured by a second weight measurement device 51. Using a weight d of the sealing body, a determination device 57 finds a weight h0 of the charged electrolyte according to an equation h0=m-m0-d.