A battery coupling method for coupling a support member (40, 90) to a battery cell, wherein (i) the support member (40, 90) is electrically insulating and has a protrusion part (43, 93) with a tip, (ii) the support member (40, 90) is configured to support the battery cell, (iii) the battery cell is provided with a group of electrodes (51, 52) accommodated in a flexible exterior member of the battery cell, wherein the exterior member is formed with a hole at a periphery side thereof, (iii') the protrusion part (43, 93) of the support member (40, 90) is configured to pass through the hole of the exterior member to thereby penetrate the hole, and (iv) the method comprises: - a placing step in which the battery cell is placed on the support member (40, 90) such that the hole of the flexible exterior member is penetrated by the protrusion part (43, 93) of the support member (40, 90); - a pressing step in which the support member (40, 90) is pressed by a pressing unit which approaches the support member (40, 90) from a side where a heating unit is positioned; - a heating step in which (a) the protrusion part (43, 93) formed on the support member (40, 90) is kept passing through the hole formed in the exterior member of the battery cell and (b) the protrusion part (43, 93) is pressed from the tip side thereof by the heating unit in order for at least a part of the tip side end of the protrusion part (43, 93) to protrude from the hole so as to form a heat-deformed part (42, 92) of a size which prevents extraction from the hole; - a heating unit separation step in which the heating unit is separated from the heat-deformed part (42, 92) after the pressing step and while the support member (40, 90) remains held pressed by the pressing unit; and - a pressing unit separation step in which the pressing unit is separated from the support member (40, 90) after the heating unit separation step. (i) the support member (40, 90) is electrically insulating and has a protrusion part (43, 93) with a tip, (ii) the support member (40, 90) is configured to support the battery cell, (iii) the battery cell is provided with a group of electrodes (51, 52) accommodated in a flexible exterior member of the battery cell, wherein the exterior member is formed with a hole at a periphery side thereof, (iii') the protrusion part (43, 93) of the support member (40, 90) is configured to pass through the hole of the exterior member to thereby penetrate the hole, and (iv) the method comprises: - a placing step in which the battery cell is placed on the support member (40, 90) such that the hole of the flexible exterior member is penetrated by the protrusion part (43, 93) of the support member (40, 90); - a pressing step in which the support member (40, 90) is pressed by a pressing unit which approaches the support member (40, 90) from a side where a heating unit is positioned; - a heating step in which (a) the protrusion part (43, 93) formed on the support member (40, 90) is kept passing through the hole formed in the exterior member of the battery cell and (b) the protrusion part (43, 93) is pressed from the tip side thereof by the heating unit in order for at least a part of the tip side end of the protrusion part (43, 93) to protrude from the hole so as to form a heat-deformed part (42, 92) of a size which prevents extraction from the hole; - a heating unit separation step in which the heating unit is separated from the heat-deformed part (42, 92) after the pressing step and while the support member (40, 90) remains held pressed by the pressing unit; and - a pressing unit separation step in which the pressing unit is separated from the support member (40, 90) after the heating unit separation step. - a placing step in which the battery cell is placed on the support member (40, 90) such that the hole of the flexible exterior member is penetrated by the protrusion part (43, 93) of the support member (40, 90); - a pressing step in which the support member (40, 90) is pressed by a pressing unit which approaches the support member (40, 90) from a side where a heating unit is positioned; - a heating step in which (a) the protrusion part (43, 93) formed on the support member (40, 90) is kept passing through the hole formed in the exterior member of the battery cell and (b) the protrusion part (43, 93) is pressed from the tip side thereof by the heating unit in order for at least a part of the tip side end of the protrusion part (43, 93) to protrude from the hole so as to form a heat-deformed part (42, 92) of a size which prevents extraction from the hole; (a) the protrusion part (43, 93) formed on the support member (40, 90) is kept passing through the hole formed in the exterior member of the battery cell and (b) the protrusion part (43, 93) is pressed from the tip side thereof by the heating unit in order for at least a part of the tip side end of the protrusion part (43, 93) to protrude from the hole so as to form a heat-deformed part (42, 92) of a size which prevents extraction from the hole; - a heating unit separation step in which the heating unit is separated from the heat-deformed part (42, 92) after the pressing step and while the support member (40, 90) remains held pressed by the pressing unit; and - a pressing unit separation step in which the pressing unit is separated from the support member (40, 90) after the heating unit separation step.