A mounting position adjustment mechanism for a rotating door that is mounted to be rotatable around a shaft includes a base member, a support member, an adjuster, and a fixing member. The base member is configured to be fixed to a door body of the rotating door. The support member is coupled to the base member at one end side of the shaft to be movable along a door surface of the rotation door in a direction orthogonal to the shaft. The adjuster is configured to adjust a position of the support member with respect to the base member in the direction orthogonal to the shaft. The fixing member is configured to fix the support member to the base member at two or more positions on the one end side of the shaft.