A battery box, comprising a lower box body, characterized in that the lower box body comprises: a first plate comprising a bottom wall and a peripheral wall that is connected to the peripheral edge of the bottom wall and extending upwards, wherein the bottom wall and the peripheral wall together form an accommodating space that opens upwards along a height direction; a second plate that is fastened under the bottom wall and that forms, together with the bottom wall, an inlet flow path, an outlet flow path, and a main flow path communicating with both the inlet flow path and the outlet flow path, wherein the main flow path comprises a first main flow path, a second main flow path, and a plurality of parallel branch flow paths that communicate with both the first main flow path and the second main flow path; the second plate comprises a plate body, wherein the plate body comprises: a first concave portion that is recessed downward from a side of the second plate facing toward the first plate; a peripheral portion that is connected to an end portion of the first concave portion and extending outward around the first concave portion; and a plurality of intermediate convex portions spaced apart along a longitudinal direction, wherein each intermediate convex portion is recessed upward from a side of the first concave portion facing away from the bottom wall and protrudes toward the bottom wall, and each intermediate convex portion is spaced apart from the periphery of the first concave portion along a traverse direction, each intermediate convex portion is provided with a run-through opening in a vertical direction; wherein the peripheral portion of the plate body and the plurality of intermediate convex portions are each in sealed connection to the bottom wall of the first plate, and the first concave portion is spaced apart from the bottom wall to form the first main flow path, the second main flow path, and the plurality of parallel branch flow paths that communicate with both the first main flow path and the second main flow path. a first plate comprising a bottom wall and a peripheral wall that is connected to the peripheral edge of the bottom wall and extending upwards, wherein the bottom wall and the peripheral wall together form an accommodating space that opens upwards along a height direction; a second plate that is fastened under the bottom wall and that forms, together with the bottom wall, an inlet flow path, an outlet flow path, and a main flow path communicating with both the inlet flow path and the outlet flow path, wherein the main flow path comprises a first main flow path, a second main flow path, and a plurality of parallel branch flow paths that communicate with both the first main flow path and the second main flow path; the second plate comprises a plate body, wherein the plate body comprises: a first concave portion that is recessed downward from a side of the second plate facing toward the first plate; a peripheral portion that is connected to an end portion of the first concave portion and extending outward around the first concave portion; and a plurality of intermediate convex portions spaced apart along a longitudinal direction, wherein each intermediate convex portion is recessed upward from a side of the first concave portion facing away from the bottom wall and protrudes toward the bottom wall, and each intermediate convex portion is spaced apart from the periphery of the first concave portion along a traverse direction, each intermediate convex portion is provided with a run-through opening in a vertical direction; wherein the peripheral portion of the plate body and the plurality of intermediate convex portions are each in sealed connection to the bottom wall of the first plate, and the first concave portion is spaced apart from the bottom wall to form the first main flow path, the second main flow path, and the plurality of parallel branch flow paths that communicate with both the first main flow path and the second main flow path. a first concave portion that is recessed downward from a side of the second plate facing toward the first plate; a peripheral portion that is connected to an end portion of the first concave portion and extending outward around the first concave portion; and a plurality of intermediate convex portions spaced apart along a longitudinal direction, wherein each intermediate convex portion is recessed upward from a side of the first concave portion facing away from the bottom wall and protrudes toward the bottom wall, and each intermediate convex portion is spaced apart from the periphery of the first concave portion along a traverse direction, each intermediate convex portion is provided with a run-through opening in a vertical direction; wherein the peripheral portion of the plate body and the plurality of intermediate convex portions are each in sealed connection to the bottom wall of the first plate, and the first concave portion is spaced apart from the bottom wall to form the first main flow path, the second main flow path, and the plurality of parallel branch flow paths that communicate with both the first main flow path and the second main flow path.