To measure a film thickness of a semiconductor of polysilicon or the like in an eddy current type film thickness measuring device.

The eddy current type film thickness measuring device 100 has a sensor coil 1 positioned at a certain distance to an object to be measured and activating an eddy current in the object to be measured by being applied with high frequency voltage, an oscillation circuit 21 supplying the high frequency voltage to the sensor coil 1, and a detection circuit 31 detecting change of inductance of the sensor coil 1 by the eddy current. Electrostatic shielding is respectively carried out to an oscillation part 20 formed with the oscillation circuit 21, and a receiving part 30 formed with the detection circuit 31. A feed-through capacitor is respectively attached to a power supply terminal 51 supplying power to the film thickness measuring device 100, and an output terminal 45 outputting a detection signal to the outside.