A work transfer apparatus includes a work carrying mechanism, a driving source that drives the work carrying mechanism, a sealed box that accommodates the driving source in a hermetically sealed state, and a coolant circulation path provided in the sealed box for cooling the driving source. The sealed box includes a box body with an opening, and a partition lid for closing the opening. The partition lid includes an outer plate member and an inner plate member superposed on the outer plate member. The coolant circulation path is disposed at the interface between the outer plate member and the inner plate member.