Substrate transfer device and method of operating the same

A substrate transfer device includes a manipulator, a substrate gripping hand, an actuator configured to rotate the substrate gripping hand about a roll axis, and a controller adapted to operate the manipulator to hold a substrate by a first engaging member and a second engaging member of the substrate gripping hand, then operate the actuator so that a first principal surface of the substrate is located above a base member, and a normal line of the first principal surface is oriented downward from a horizontal plane, and move a movable guiding member toward the tip-end part of the base member so that the second engaging member, a third engaging member, and the movable guiding member grip the substrate.