To provide a construction method for a soundproof panel, which simplifies construction when the soundproof panel is constructed on a road and at the periphery thereof, and a locking implement for use in the construction method.

The locking implement 1, which is hung down by means of a hanger 2, is locked to an inner end of a notch which is provided at each of the right and left ends of the top surface of the soundproof panel, and the soundproof panel is hung down and dropped in between recessed grooves of a support. After that, the locking implement 1 can easily be pulled out from the notch by unlocking the hanger 2 from the inner edge of the notch. This makes it unnecessary for the hanger to be pulled out by lifting the bottom part of the soundproof panel by means of an implement such as a crowbar, as in a conventional construction method for the soundproof panel, enables the simple construction of the soundproof panel, and enables the shortening of a construction time for the soundproof panel.