A connecting device adapted to connect a first wall to one of two second walls of a furniture piece , the connecting device characterized by : a base portion connectable to the first wall of the furniture piece , wherein the base portion comprises a surface and a space adjacent to the surface ; and an opening of the space is located at the surface , and at least one engaging arm arranged at the base portion , the at least one engaging arm being resiliently movable around a hypothetical axis (X), and the at least one engaging arm being arranged with an engaging portion , wherein the at least one engaging arm is arranged inside the space , and a length of the at least one engaging arm does not exceed the surface ; an auxiliary portion substantially perpendicularly connected to the base portion , wherein the auxiliary portion comprises at least one fastening feature provided to be inserted by a fastening member . wherein the hypothetical axis (X) is substantially parallel to the first wall when the device is connected to the furniture piece ; wherein one of the second walls of the furniture piece is mountable to the engaging portion along a mounting direction (Y) via a mounting portion , arranged and adjacent to an end portion of the second wall upon connection and detachably mounted to the engaging portion ; wherein the mounting direction (Y) is substantially perpendicular to the hypothetical axis (X); wherein an end of the other second wall of the furniture piece is capable of abutting against the surface of the base portion , and the second wall of the furniture piece may be fixed to the auxiliary portion via the at least one fastening feature and the fastening member . a base portion connectable to the first wall of the furniture piece , wherein the base portion comprises a surface and a space adjacent to the surface ; and an opening of the space is located at the surface , and at least one engaging arm arranged at the base portion , the at least one engaging arm being resiliently movable around a hypothetical axis (X), and the at least one engaging arm being arranged with an engaging portion , wherein the at least one engaging arm is arranged inside the space , and a length of the at least one engaging arm does not exceed the surface ; an auxiliary portion substantially perpendicularly connected to the base portion , wherein the auxiliary portion comprises at least one fastening feature provided to be inserted by a fastening member . wherein the hypothetical axis (X) is substantially parallel to the first wall when the device is connected to the furniture piece ; wherein one of the second walls of the furniture piece is mountable to the engaging portion along a mounting direction (Y) via a mounting portion , arranged and adjacent to an end portion of the second wall upon connection and detachably mounted to the engaging portion ; wherein the mounting direction (Y) is substantially perpendicular to the hypothetical axis (X); wherein an end of the other second wall of the furniture piece is capable of abutting against the surface of the base portion , and the second wall of the furniture piece may be fixed to the auxiliary portion via the at least one fastening feature and the fastening member . <EOS>