To provide a measuring device which can easily measure the thickness of a film formed on a recessed part or the inside of a tube.

A film thickness measuring device has a long lengthened bar- shaped housing 10. The one end part of the housing 10 is provided with a display section 11 for displaying the result of measurement. In the case of measuring a film formed on the inside of a tube, the housing 10 is inserted inside the tube 23 with a measuring probe 17 provided in the end part of the housing inclined about as much as 90 degrees. The measured film inside the tube can be measured with a measuring pole 19 located in the bottom part of the measuring probe 17 standing perpendicularly to the film to be measured, and the result of measurement can be read out from a display section 11.