A method of manufacturing a power storage module includes: stacking a plurality of power storage cells along a first direction; compressing the plurality of power storage cells along the first direction; aligning the plurality of power storage cells in a second direction orthogonal to the first direction after relieving pressing force of the compressing; compressing the plurality of power storage cells along the first direction after aligning the plurality of power storage cells in the second direction; disposing a restraint portion on both sides in the first direction with respect to the plurality of power storage cells under application of pressing force of the compressing; and restraining the plurality of power storage cells by the restraint portion along the first direction by relieving, after disposing the restraint portion, the pressing force of the compressing.