Provided is a thermal conduction sheet that is easily attached from one face to the other face of a battery cell, the faces being perpendicular to each other. Thermal conduction sheet includes graphite sheet, and insulating sheets between and with which graphite sheet is entirely sandwiched and sealed. Graphite sheet has a plurality of cut-out portions arranged linearly. Thermal conduction sheet is bent at a region where cut-out portions are formed. Thus, thermal conduction sheet is attached from one face to the other face of a battery cell, the faces being perpendicular to each other.