To provide a locking structure of a folding leg column that can release the locking of each leg column by pushing down a lock lever in the nearly same waiting posture whether it is in unfolded state or in folded state of the leg column.

This locking structure is made of a support bracket which is fixed to a top plate and on one side of which the leg column is pivotally supported, a lock lever which is pivotally supported on the other side of the support bracket and has a locking part at one end and an operating member at the other end, and is energized in the locking direction, and a locking cam which is fixed to the leg column and is provided so that the locking part of the lock lever contacts constantly. The locking cam comprises a folding lock receiving part and an unfolding lock receiving part and can hold the lock lever in the nearly same waiting posture at the unfolding time and folding time of the leg column.