The present invention provides a waterproof structure excellent in handleability of a storage box installed outdoors. A plurality of flat plates A, C, and D provided in parallel are fixedly held by sealing materials made of rubber or synthetic rubber at adjoining portions along the longitudinal direction and adjacent outer surfaces of the endmost flat plates. On one side of the flat plate adjacent to the longitudinal direction is a projecting piece 6 and a retaining piece 7 for the first sealing material B vertically provided below the tip of the projecting piece and the side surface. has a holding portion 5 provided with a gripping piece 8 of the first sealing material facing approximately 45 degrees upward at the bottom edge of the holding portion 5, and a receiving projecting piece for receiving the tip of the projecting piece on the other side surface 10, a second holding piece 11 of the first sealing material vertically provided at the extreme end of the receiving projecting piece, and a contact piece provided on the front surface of the second holding piece are integrally provided, and The lowermost edge has a second holding portion 9 provided with a second gripping piece 13 of the first sealing material directed approximately 45 degrees upward, and the flat plate adjacent to the endmost flat plate has a second holding portion 9. It is assumed that there is provided a groove-shaped mounting portion 18 for the second seal member E on the outer side surface where there is no groove. [Selection drawing] Fig. 4【課題】屋外に設置される収納ボックスの取り扱い性に優れた防水構造を提供する。【解決手段】平行に設けられた複数の平板A、C、Dの長手方向に沿った隣接箇所及び*端部となる平板の隣接する外側面にゴムまたは合成ゴム製のシール材を固定保持させてあることとし、平板の長手方向に沿った隣接箇所となる側面には一方側には突片6とその突片の先端側下方に垂設された**シール材Bの保持片7と側面の*下縁には略45度上方に向けた**シール材の握持片8とを備えた保持部5を有しており、他方側の側面には突片の先端を受ける受け突片10と、その受け突片の*先端に垂設された**シール材の第二の保持片11と、その第二の保持片の前面に設けられた当接片を一体に設け、かつ、*下縁には略45度上方に向けた**シール材の第二の握持片13が備えられている第二の保持部9を有し、*端部となる平板の隣接する平板の無い外側面には溝状とした第二シール材Eの取り付け部18を有していることとする。【選択図】図4