An embodiment of this application provides a device and method for assembling a battery cell. The device includes: a conveyance mechanism, configured to fix an electrode assembly and convey the electrode assembly to a coating station; a coating mechanism, configured to coat at least a part of an outer surface of the electrode assembly with an insulation layer at the coating station, where the conveyance mechanism is further configured to: convey the electrode assembly coated with the insulation layer to an encasing station; and an encasing mechanism, configured to fit, at the encasing station, a housing peripherally onto the electrode assembly coated with the insulation layer. The device and method for assembling a battery cell disclosed herein can improve the assembling efficiency of battery cells.