PROBLEM TO BE SOLVED: To provide a bird damage prevention device that can be installed in a short time.SOLUTION: A bird damage prevention device 101 has: a main line mounting part mountable to a main line disposed in air a slide base part 107 extending along a first axis FA that is a direction perpendicular to the axis of the main line when the main line mounting part is mounted a slide part 3 slidably formed to the slide base part 107 and a slide control part 5 capable of changing a slidable state and an unslidable state between the slide base part 107 and the slide part 3. The slide part 3 or the slide control part 5 is formed to hold a sub-line W for bird repellent. The slide base part 107 and the slide part 3 are slidable over the first axis FA. The slide control part 5 is rotated centering on a second axis SA by a user, and thereby is changed between the slidable state and the unslidable state. The first axis FA and the second axis SA have a skewed relationship.
