An object is to provide, in place of a cube toy such as Yoshimoto Cube, a wide variety of playing patterns, playing patterns which cannot be predicted in terms of change in forms, a polyhedral toy which can be enjoyed in terms of change in form even when only one polyhedral toy is used, and a polyhedral toy having extensibility for achieving a wide variety of contents of play through combination of two or more polyhedral toys. Therefore, when a polyhedral piece (U