| A rotational structure (10) comprises a base member (11), a shaft member (12) and a rotational member (13). The shaft member (12) includes one end fixed to the base member (11) and extends in an axial direction of the rotational structure (10). The rotational member (13) is attached to the shaft member (12) through a bearing (16) and configured to rotate about the shaft member (12). At least one of the base member (11) and the rotational member (13) is provided with a coupling surface (32) serving as a plane to couple a different member, in an external circumferential surface thereof in a circumferential direction of the shaft member (12). The coupling surface (32) is provided with a groove portion (32A) having a cross section with an inverted T shape. |
