A tab threading device for a battery, and an assembly apparatus are disclosed. The battery comprises a case and an electrode assembly, wherein the case is provided with an accommodating cavity and through holes. The tab threading device is used for guiding tab parts of the electrode assembly to extend out through the through holes. The tab threading device comprises a clamping mechanism and a driving mechanism, wherein the clamping mechanism comprises a first clamping member and a second clamping member; and the driving mechanism is configured to drive the first clamping member and/or the second clamping member to move, so that the first clamping member and the second clamping member can clamp the tab parts to pass through the through hole and extend from the accommodating cavity.