A numerical controller which, after once stopping a slave axis during superposing control, can easily resume the superposing control. In the superposing control, a motion amount for a master axis and a motion amount for the slave axis are added to a workpiece coordinate value of the master axis and a workpiece coordinate value of the slave axis, respectively, to update their present position data (I2, II2). These motion amounts are supplied also to servo processing (I3, II3) for the master axis and the slave axis, where an amount obtained by superposing a motion amount .delta.zIm for the master axis ZIm on a motion amount .delta.zIIs for the slave axis ZIIs is supplied to the servo processing for the slave axis ZIIs. When a slave axis motion stop command is issued, the motion of the slave axis is stopped and a motion amount .delta.zIm for the master axis ZIm is subtracted from the workpiece coordinate value of the slave axis ZIIs. This makes it possible to retain the positional relationship between the master axis and the slave axis, and hence easily resume the superposing control when the motion of the slave axis is restarted.