Abstract: An overhead hoist transfer apparatus includes a rail assembly including a straight rail having an empty section, and a curved rail having a curved empty section; an engine including a first LSD having first and second wheels at two sides respectively; and a second LSD having third and fourth wheels at two sides respectively; a moving carriage driven by the engine and suspended from the rail assembly; first and second guide wheels disposed on the first LSD; third and fourth guide wheels disposed on the second LSD; and two guide boards disposed above a joining point of the straight rail and the curved rail. An elevation of the guide boards is equal to that of the guide wheels. The guide board includes a straight edge and a curved edge.