Keyaki wood is the most suitable material for the “Wadaiko, a traditional Japanese drum.” However, the amount of wood with excellent quality available for producing the wadaiko has decreased in recent years. Wadaiko shells made of artificial materials are an effective substitute for the traditional wooden wadaiko. In this study, prototypes of the wadaiko were made using a wood plastic and their sound characteristics were examined. The vibrational properties of the wood plastic were investigated and compared with those of keyaki and sen woods used for the traditional wooden wadaiko. The sound characteristics of the wood plastic wadaiko were more complex than those of the keyaki wadaiko. The Chladni experiment on the wood plastic wadaiko clarified that the respective modal patterns appeared at two or three resonant frequencies with increasing the degree of the modes. The sound components of the wood plastic shell did not affect the overall sound characteristics of the wadaiko. The internal friction of wood plastic was larger than those of keyaki and sen, whereas the specific Young’s modulus in the grain direction was smaller than those of keyaki and sen. The results of this study indicated that the mechanical properties of wadaiko shell materials strongly affected both the tension of the membrane and the boundary condition between the membrane and shell. A large specific Young’s modulus as well as high strength comparable to that of keyaki is necessary for wood plastics to be used as a substitute material for the wadaiko shell.