An on-load tap changer of a step switch has a force-storage unit which has a charging slide continuously movable by a bidirectionally rotatable drive shaft and an output part that when tripped suddenly follows the movement of the charging slide and rotates a switching shaft. Respective switches for each phase are each actuatable by respective actuating elements that coact with edges of respective concentric cams rotatable by the switching shaft. An axially movable switching unit is mounted on the switching shaft and the switching unit carries cam disks for actuating the switches, each cam disk being subdivided into an upper and a lower subdisk with different shapes. The switching unit is movable in a direction dependent on the rotation direction of the drive shaft into an upper or a lower position. In the upper position of the switching unit all of the lower cam subdisks and in the lower position of the switching unit all of the upper cam subdisks engage the actuating elements to actuate the respective switches.