A pressurization device (10, 100) for battery cells which pressurizes, in a thickness direction of the battery cell, a plurality of the battery cells, in each of which a power generation element is sealed with a liquid electrolyte in an exterior body made of a laminated film, having thin flat shapes in the thickness direction, comprising: a housing (11, 110) accommodating the plurality of the battery cells; a plurality of spacers arranged in the thickness direction, supported by the housing (11, 110) and forming bag shapes which are capable of expanding and contracting in at least the thickness direction in accordance with fluid pressure of working fluid sealed inside the spacers; and a pressure supply passage (22, 220) used for supplying the fluid to the plurality of the spacers from a fluid pressure source, wherein each space larger than dimensions of the battery cells in the thickness direction is maintained between adjacent spacers in a state in which the spacers have been contracted by decreasing the fluid pressure inside the spacers, and wherein the battery cells, each of which is arranged between the adjacent spacers, are pressurized in the thickness direction in a state in which the spacers have been expanded by increasing the fluid pressure inside the spacers, characterized in that the spacer is equipped with cell supporting portions (37, 38, 39) that are opposed to the exterior body in a position outside the power generation element of the battery cell along the thickness direction, the cell supporting portions (37, 38, 39) are provided at a peripheral edge portion of the spacer that is not expanded, and upper end portions (37a, 38a, 39a) of the respective cell supporting portions (37, 38, 39) are formed into tapered shapes tapering off toward a direction opposite to an insertion direction of the battery cell. a housing (11, 110) accommodating the plurality of the battery cells; a plurality of spacers arranged in the thickness direction, supported by the housing (11, 110) and forming bag shapes which are capable of expanding and contracting in at least the thickness direction in accordance with fluid pressure of working fluid sealed inside the spacers; and a pressure supply passage (22, 220) used for supplying the fluid to the plurality of the spacers from a fluid pressure source, wherein each space larger than dimensions of the battery cells in the thickness direction is maintained between adjacent spacers in a state in which the spacers have been contracted by decreasing the fluid pressure inside the spacers, and wherein the battery cells, each of which is arranged between the adjacent spacers, are pressurized in the thickness direction in a state in which the spacers have been expanded by increasing the fluid pressure inside the spacers, characterized in that the spacer is equipped with cell supporting portions (37, 38, 39) that are opposed to the exterior body in a position outside the power generation element of the battery cell along the thickness direction, the cell supporting portions (37, 38, 39) are provided at a peripheral edge portion of the spacer that is not expanded, and upper end portions (37a, 38a, 39a) of the respective cell supporting portions (37, 38, 39) are formed into tapered shapes tapering off toward a direction opposite to an insertion direction of the battery cell.