A position/force control device includes position detectors on a master 1 side and on a slave 3 side. Reaction force estimation observers 2 and 4 estimate reaction force based on outputs of the position detectors. A position control part 5 generates acceleration signals apm, aps for controlling positions on the master side and on the slave side on the basis of the position signals outputted by the position detectors. The operation force control part 6 generates acceleration signals afm, afs for controlling forces applied to the master side and to the slave side based upon the outputs from reaction force estimation observers 2 and 4. The acceleration composition part 7 composes the two sets of acceleration signals apm, aps, and afm, afs, and outputs the driving signals for the master side and the slave side.