A method of manufacturing a stacked stator core comprises forming a stack that comprises an annular yoke portion, a plurality of tooth portions, and a plurality of slots. The method further comprises inserting a mold core member of the plurality of mold core members into a slot of the plurality of slots, the mold core member comprising a body portion and a closing portion connected to the body portion, the body portion extending along a longitudinal direction of the slot and spaced apart from an inner wall surface of the slot, the closing portion being positioned on a slot opening side of the slot and closing an open end portion of the slot on the slot opening side. Additionally, the method comprises forming a resin portion by charging a melted resin into a filling space between the slot and the mold core member.