To provide an improved partition board connecting device capable of more accurately connecting partition boards together and of enhancing the appearance of a partition wall.

A device which connects together panel-shaped partition boards each having a rectangular plane and horizontal long sides, for forming a partition wall, comprises two metallic parts for coupling a lower partition board A to an upper partition board B. One of the metallic parts, PA, is mounted on the upper horizontal long side of the lower partition board A, while the other metallic part B is mounted on the lower horizontal long side of the upper partition board B, the metallic parts PA, PB being coupled together by a tongue- and-groove joint; once the metallic parts are coupled together, the desired recess S which accommodates and holds an element or fastener extending along the horizontal long sides of the partition boards A, B and projecting from the partition wall, or which accommodates and holds the corresponding part of an element or fastener for hanging on a wall is formed.