NOVELTY - The pack (10) has a battery cell unit (21) whose lead element (35) is connected to circuit board (22). Joint surface portions (47A,47B) are formed in inner surfaces of pack elements (44A,44B) and mutually bonded together to form outer edge portion (50). A waterproof pack element (43) is arranged to accommodate cell unit and board. A lead wire (26) of board is arranged to connect external electrode of lead element and waterproof pack element. The wire is withdrawn by exterior of waterproof pack element in state pinched into surface portions, and fixed by edge portion.    USE - Battery pack of battery module for electrically-driven type vehicle such as two-wheeled vehicle such as electric-power-assisted bicycle, and four-wheeled vehicle.    ADVANTAGE - The joint surface portions are formed in inner surfaces of pack elements and mutually bonded together to form outer edge portion, so that the excessive portion is produced at edge portion of outer edge portion, thus formation of clearance gap can be eliminated effectively. Hence, the high water tightness can be ensured by bonding pack elements together without gap uniformly. The cell unit and board are accommodated watertight in waterproof pack element inside with outer edge portion, so that favorable waterproofness of cell unit and accommodation location of board can be secured in long run. The freedom degree of pull-out position of lead wire can be made high. Since the exterior of waterproof pack element withdraws in state to which wire is pinched into joint surface portions and fixed watertight, the load is reduced in joint surface of joint surface portions, even if local force is added to wire, while preventing fracture by contact portion of board and wire. The battery pack with high working efficiency can be provided effectively.    DESCRIPTION OF DRAWING(S) - The drawing shows an exploded perspective view of the battery pack.    Battery pack (10)    Battery cell unit (21)    Circuit board (22)    Lead wire (26)    Lead element (35)    Waterproof pack element (43)    Pack elements (44A,44B)    Joint surface portions (47A,47B)    Outer edge portion (50)