Connecting construction of cam sprocket

The invention provides a connecting construction of a cam sprocket capable of easily performing positioning of a cam sprocket and a camshaft. The connecting structure of a cam sprocket connects a cam sprocket to an end surface of a camshaft, and the cam sprocket is used for erecting a timing chain transmitting power of a crankshaft to the camshaft, wherein, on the cam shaft, a first positioning pin hole and bolt holes are formed in a communication from the end surface of the camshaft toward the center of the camshaft on a rotating central line; a second positioning pin hole is formed at the center of the cam sprocket; a camshaft and a cam sprocket are positioned via cylindrical positioning pins embedded into the first and second positioning pin holes, and are connected via bolts through the inner periphery of the positioning pins and screwed with the bolt holes.