A battery module comprising: a plurality of battery cells arranged side by side in a first direction, each of the plurality of battery cells having a prismatic shape; a restraint mechanism (400, 500) that restrains the plurality of battery cells in the first direction; and a restraint force adjustment mechanism (900, 1000) capable of adjusting a restraint load in the first direction, the restraint load being applied by the restraint mechanism (400, 500), wherein the restraint force adjustment mechanism (900, 1000) includes an operation portion (920, 1010) to be operated when adjusting the restraint load (400, 500), the operation portion (920, 1010) is provided on the battery module, the restraint mechanism (400, 500) includes two end plates provided at both end portions of a stack of the plurality of battery cells in the first direction, and a binding bar that connects the two end plates to each other, i) the restraint force adjustment mechanism includes: at least one bolt member attached to one of the two end plates along the first direction, and a nut member screwed on the bolt member, and one of the two end plates is able to be deflected toward the stack by fastening the nut member onto the bolt member, and an amount of deflection of one of the two end plates is able to be adjusted by adjusting an amount of fastening of the nut member, or ii) the restraint force adjustment mechanism includes a bolt member extending through the binding bar along a second direction orthogonal to the first direction and fastened to another component of the battery module, and by adjusting a fastening force of the bolt member, an amount of deflection of the binding bar along the second direction is able to be adjusted to adjust a length of the battery module along the first direction. a plurality of battery cells arranged side by side in a first direction, each of the plurality of battery cells having a prismatic shape; a restraint mechanism (400, 500) that restrains the plurality of battery cells in the first direction; and a restraint force adjustment mechanism (900, 1000) capable of adjusting a restraint load in the first direction, the restraint load being applied by the restraint mechanism (400, 500), wherein the restraint force adjustment mechanism (900, 1000) includes an operation portion (920, 1010) to be operated when adjusting the restraint load (400, 500), the operation portion (920, 1010) is provided on the battery module, the restraint mechanism (400, 500) includes two end plates provided at both end portions of a stack of the plurality of battery cells in the first direction, and a binding bar that connects the two end plates to each other, i) the restraint force adjustment mechanism includes: at least one bolt member attached to one of the two end plates along the first direction, and a nut member screwed on the bolt member, and one of the two end plates is able to be deflected toward the stack by fastening the nut member onto the bolt member, and an amount of deflection of one of the two end plates is able to be adjusted by adjusting an amount of fastening of the nut member, or ii) the restraint force adjustment mechanism includes a bolt member extending through the binding bar along a second direction orthogonal to the first direction and fastened to another component of the battery module, and i) the restraint force adjustment mechanism includes: at least one bolt member attached to one of the two end plates along the first direction, and a nut member screwed on the bolt member, and one of the two end plates is able to be deflected toward the stack by fastening the nut member onto the bolt member, and an amount of deflection of one of the two end plates is able to be adjusted by adjusting an amount of fastening of the nut member, or at least one bolt member attached to one of the two end plates along the first direction, and a nut member screwed on the bolt member, and ii) the restraint force adjustment mechanism includes a bolt member extending through the binding bar along a second direction orthogonal to the first direction and fastened to another component of the battery module, and by adjusting a fastening force of the bolt member, an amount of deflection of the binding bar along the second direction is able to be adjusted to adjust a length of the battery module along the first direction.