Abstract: The present invention relates to an arrangement in connection with a control device (1) particularly used for controlling a forestry machine and a boom thereof. The control device comprises a frame section (5), a handle (2) attached pivotally thereto, operating switches (3) at the handle and a control keyboard (4) arranged in connection with the handle onto a supporting plate (8) surrounding the handle. The present invention enables a driver to reach all control keys (9) of the control device at all operating positions of the control device. Thus the supporting plate comprises a dome-shaped element having, for example, spherical outer surface (10) and being arranged in connection with the handle (2). The control keyboard (4) is arranged on the outer surface of this element.