To provide a locking mechanism for engaging and retaining an engaging hook that is biased upward by a spring, wherein even when retaining an object to be carried such as a coating tank having a cylindrical protrusion formed on a lower end side thereof, the engaging hook can be removed smoothly without getting snagged inside the protrusion.

The locking mechanism is provided which keeps a spring (5) for biasing an engaging hook (6) upward in a lever form capable of rotating around a fulcrum (PC) disposed at a midpoint of an action point (PF) and a power point (PE) when one end side of the spring (5) having the engaging hook (6) is employed as the action point (PF) and the other end side of the spring (5) as the power point (PE). The engaging hook (6) is retreated below a lower end position of the object to be carried by its own weight in a state that no external force is exerted, and simultaneously moved upward from and disposed at the lower end position of the object to be carried so that the power point (PE) is in contact with a front end side (2F) in a direction of pushing the object to be carried (2).