The vertical and angular position adjusting device includes at each lateral side of the seat a five-bar linkage including an underframe, a seat carrier bar, a pair of two-arm support levers pivotably connected to the frame, a coupling bar linked between the outer arm of one of the support levers and an end portion of the carrier bar, and the other end portion of the carrier bar being hinged to the outer arm of the other support lever. The support levers at one lateral side of the seat have gear segments formed on the inner arm of each support lever. A pair of arresting levers is linked to the underframe between the support levers and is provided with arresting teeth engageable with respective gear segments. A pair of switching levers is linked to the underframe between the arresting levers and is spring-biased to abut against a front locking surface provided on each arresting lever in order to hold the latter in a locking position. A control lever is linked to the underframe between the switching levers and supports a cam which displaces the switching levers against the force of the spring into a released position in which the selected arresting lever is disengaged from the support lever.