In a secondary air supplying structure of an internal combustion engine, extending portions protruding upward are arranged in the number corresponding to the number of cylinders. Extending portions are each provided with a secondary air distribution path. To a surface of extending portion to which secondary air supplying pipe abuts, a seating face that conforms to the outer shape of secondary air supplying pipe is formed. Secondary air distributing path is arranged to be inclined downwardly from secondary air supplying pipe side toward the cylinder exhaust system of cylinder head. Thus, it is possible to provide the secondary air supplying structure of an internal combustion engine that can attain an improvement in the strength of the secondary air supplying path, reduction of the space, rust prevention, reduced costs, reduced weight, simplified structure, and prevention of thermal damage to other components.