To provide a locking device which can be installed with ease to an existing lever handlebar provided to a door, can lock a swing operation of the lever handlebar, and can easily be canceled a locked state when the lever handlebar is used.

A locking device comprises: a lever handlebar 15 whose rotatable lever shaft 23 protrudes perpendicularly from a door surface 21 and whose lever grip part 31 perpendicular to the lever shaft 23 swings so as to enable a door 25 to be unlocked; an operation barrier member 17 which extends along the lever grip part 31 at an opposite side to a rotating direction of the lever grip part 31 so as to block a rotating operation of the lever grip part 31; and a barrier member supporting body 19 which includes a supporting shaft 35 perpendicular to the lever shaft 23, is fixed to the door 25, and supports swingably an end portion 41 of the operation barrier member 17 in a longitudinal direction with the supporting shaft 35.