To provide a strut waterproof structure which can perform waterproof construction in the peripheral part of the strut members without necessity of any special skills.SOLUTION: This strut waterproof structure waterproofs the peripheral part of the strut member 82 protruding from an opening 81 formed in an outdoor flat ground part 80. This strut waterproof structure includes a flat-field waterproofing accessory 1 having a flat-side sheet part 1a located on the upper surface of the flat-field part 80 around the strut member 82 and a strut-side sheet part 1b covering the lower surface of the strut member 82, a secondary waterproof tape part 3 that seals the boundary between the strut side sheet portion 1b and the surface of the strut member 82 as a secondary waterproof part, an upper waterproof accessory 2 covered so that the upper side is located on the surface of the secondary waterproof tape part 3 and a primary waterproof tape part 5 that seals the boundary between the upper side of the upper waterproof accessory 2 and the surface of the strut member 82 as a primary waterproof part.SELECTED DRAWING: Figure 1