PURPOSE: To firmly and economically join FRP material of insulating body with copper material or copper alloy material to be prevented from sticking of seaweads, shell fish, etc.
CONSTITUTION: The water contact face side making contact with water is made of copper material or copper alloy material 1, and the water non-contact face side joined with the copper material or the copper alloy material and not contacting with water is made of FRP material 2 of insulating body. Adhesive 3 of unsaturated polyester resin added with nitrogen compound such as dimethylethyl-aniline is spread on the contact surface of the copper material or the copper alloy material 1 so as to join with the FRP material 2, and hence copper-FRP bonded material 4 having sufficient adhesive strength is formed.