To provide a corrosion prevention structure of a steel pipe sheet pile, which allows a number of auxiliary covers for covering joints to be easily fixed.

This corrosion prevention structure comprises brackets 4 which are fastened to the vicinity of a joint 2 between neighboring steel pipes 1a, approximately opposing to each other; an anticorrosive cover panel 5 which is fixed to the bracket so as to cover the sea side of the steel pipe; bottom plates 7a and 7b which are fastened to the steel pipes; and an anticorrosive auxiliary cover 10 which covers the joint 2. The cover panel 5 is provided with claws 17 at both ends. The auxiliary cover 10 made of flexible material has an approximately V-shaped cross section. The auxiliary cover 10 has a medially located bent part and both sides engaged with the claws 17 and 17.