Abstract: A stand rotating mechanism having a high strength and a high durability and being rotatable 90.degree. for each of right and left sides. The stand rotating mechanism includes a rotary base, and a rotary base supporting base for rotatably supporting the rotary base. The rotary base includes locking members and a guide slot on and in the convex surface thereof. The rotary base supporting base includes on its concave surface a rotating shaft to be inserted in the guide slot and members to be locked. The locking members are abutted on the members to be locked in accordance with a rotational state of the rotary base, to restrict the rotation of the rotary base.