A busbar module, comprising: a plurality of busbars configured to be fixed to a plurality of battery cells of a battery module including the plurality of battery cells; a plate-like flexible circuit body that includes a plurality of connection conductors corresponding to the plurality of busbars; and a case that accommodates the circuit body and the busbars, wherein the circuit body includes a trunk portion extending in a first direction in which the plurality of battery cells are arranged, and a plurality of branch portions branching from the trunk portion and connected to the busbars, the branch portion includes a base portion connected to the trunk portion, a fixed portion fixed to the busbar, and an intermediate portion extending from the base portion to the fixed portion in the first direction, and being curved in a desired S-shape, a first end portion of the trunk portion in the first direction has a first through-hole, and the case includes a first bridge portion and a first protrusion inserted into the first through-hole, and locks the first end portion with the first protrusion to hold the circuit body in a state where the intermediate portion is flexurally deformed, characterized in that the first protrusion includes a shaft portion and an eaves portion, the shaft portion being a proximal end portion of the first protrusion and having a columnar shape along a height direction of the battery cells orthogonal to the first direction, and the eaves portion protruding from a distal end of the shaft portion and having a columnar shape along the height direction, wherein the shaft portion is connected to the first bridge portion, and wherein the eaves portion is positioned on an axis different from an axis of the shaft portion and is eccentric with respect to the shaft portion so that the eaves portion is shifted with respect to the shaft portion in the first direction, and the outer diameter of the shaft portion is equal to an inner diameter of the first through-hole, wherein the eaves portion protrudes in a direction opposite to a direction of a reaction force generated by the branch portion. a plurality of busbars configured to be fixed to a plurality of battery cells of a battery module including the plurality of battery cells; a plate-like flexible circuit body that includes a plurality of connection conductors corresponding to the plurality of busbars; and a case that accommodates the circuit body and the busbars, wherein the circuit body includes a trunk portion extending in a first direction in which the plurality of battery cells are arranged, and a plurality of branch portions branching from the trunk portion and connected to the busbars, the branch portion includes a base portion connected to the trunk portion, a fixed portion fixed to the busbar, and an intermediate portion extending from the base portion to the fixed portion in the first direction, and being curved in a desired S-shape, a first end portion of the trunk portion in the first direction has a first through-hole, and the case includes a first bridge portion and a first protrusion inserted into the first through-hole, and locks the first end portion with the first protrusion to hold the circuit body in a state where the intermediate portion is flexurally deformed, characterized in that the first protrusion includes a shaft portion and an eaves portion, the shaft portion being a proximal end portion of the first protrusion and having a columnar shape along a height direction of the battery cells orthogonal to the first direction, and the eaves portion protruding from a distal end of the shaft portion and having a columnar shape along the height direction, wherein the shaft portion is connected to the first bridge portion, and wherein the eaves portion is positioned on an axis different from an axis of the shaft portion and is eccentric with respect to the shaft portion so that the eaves portion is shifted with respect to the shaft portion in the first direction, and the outer diameter of the shaft portion is equal to an inner diameter of the first through-hole, wherein the eaves portion protrudes in a direction opposite to a direction of a reaction force generated by the branch portion.