In a simultaneous multi-axis measuring machine tool system including linear drive axes and rotation axes to measure a surface shape of an object to be measured by using an on-board measuring device having a probe mounted, at one end thereof, with a spherical contactor, a numerical controller controls driving of the linear drive axes and the rotation axes so that a central axis of the probe is always oriented in a direction perpendicular to the surface of the object to be measured and that the spherical contactor of the probe comes in contact with and follows a surface of the object to be measured.