A battery module comprising: a plurality of batteries each including an outlet of a discharge valve disposed in a projecting electrode on an end face of each of the plurality of batteries, the discharge valve being configured to open when an internal pressure of each of the plurality of batteries rises to a set pressure; a battery holder arranging the plurality of batteries parallel to each other at fixed positions; a lead plate connected to the projecting electrode of each of the plurality of batteries that are arranged at the fixed positions by the battery holder, the end face of each of the plurality of batteries being disposed on a same plane; and a potting resin thermally coupled to the lead plate, wherein the battery holder includes an outer peripheral cover having an electrode window to expose the projecting electrode and being disposed on a plane facing an outer peripheral edge of the projecting electrode, the lead plate includes: a planar part disposed over a surface of the outer peripheral cover; and a connection recess disposed in the planar part, the connection recess being guided into the electrode window in the battery holder and protruding toward the projecting electrode to connect a protrusion face of the connection recess to the projecting electrode, a first double-sided tape provides a tight fit between an outer peripheral part of each of the plurality of batteries and the outer peripheral cover of the battery holder to ensure that the outer peripheral part of each of the plurality of batteries fits tightly over the outer peripheral cover, a second double-sided tape provides a tight fit between the outer peripheral cover of the battery holder and the planar part of the lead plate to ensure that the outer peripheral cover fits tightly over the planar part of the lead plate, a sealing label is put into intimate contact with the planar part of the lead plate to ensure that the sealing label closes an opening of the connection recess of the lead plate, and the first double-sided tape, the second double-sided tape, and the sealing label constitute a structure that prevents the potting resin from flowing into the outlet disposed in the projecting electrode. a plurality of batteries each including an outlet of a discharge valve disposed in a projecting electrode on an end face of each of the plurality of batteries, the discharge valve being configured to open when an internal pressure of each of the plurality of batteries rises to a set pressure; a battery holder arranging the plurality of batteries parallel to each other at fixed positions; a lead plate connected to the projecting electrode of each of the plurality of batteries that are arranged at the fixed positions by the battery holder, the end face of each of the plurality of batteries being disposed on a same plane; and a potting resin thermally coupled to the lead plate, wherein the battery holder includes an outer peripheral cover having an electrode window to expose the projecting electrode and being disposed on a plane facing an outer peripheral edge of the projecting electrode, the lead plate includes: a planar part disposed over a surface of the outer peripheral cover; and a connection recess disposed in the planar part, the connection recess being guided into the electrode window in the battery holder and protruding toward the projecting electrode to connect a protrusion face of the connection recess to the projecting electrode, a planar part disposed over a surface of the outer peripheral cover; and a connection recess disposed in the planar part, the connection recess being guided into the electrode window in the battery holder and protruding toward the projecting electrode to connect a protrusion face of the connection recess to the projecting electrode, a first double-sided tape provides a tight fit between an outer peripheral part of each of the plurality of batteries and the outer peripheral cover of the battery holder to ensure that the outer peripheral part of each of the plurality of batteries fits tightly over the outer peripheral cover, a second double-sided tape provides a tight fit between the outer peripheral cover of the battery holder and the planar part of the lead plate to ensure that the outer peripheral cover fits tightly over the planar part of the lead plate, a sealing label is put into intimate contact with the planar part of the lead plate to ensure that the sealing label closes an opening of the connection recess of the lead plate, and the first double-sided tape, the second double-sided tape, and the sealing label constitute a structure that prevents the potting resin from flowing into the outlet disposed in the projecting electrode.