Provided are a heat exchanger capable of cooling a shell plate and having good assemblability and a hot water apparatus having the same. A primary heat exchanger includes a heat exchanging portion, a shell plate, and a shell pipe portion. The shell plate surrounds the heat exchanging portion. The shell pipe portion is for cooling the shell plate. The shell plate includes a front surface portion and a main body portion. The main body portion is installed on the front surface portion and is formed by bending one sheet of plate into a U shape. The shell pipe portion is bent in a U shape along an inner surface of the main body portion and installed on the inner surface.