To provide a work seating confirmation device of machine tool, confirming seating of a work to a spindle chuck even when the spindle chuck side is not provided with a work seating confirming function.

This work seating confirming device is composed of a loader 11 for transferring a work W to the machine tool 1 and a seating confirming means 10 for detecting whether or not the work is seated on a work seating surface 3b of the machine tool 1 when the loader 11 delivers the work W. The loader 11 includes a loader head 16 freely moved opposite to the work seating surface 3b. The loader head 16 is provided with a chuck 17A for holding the work W, a pusher 19 for pushing the work W. and a work position detecting means 22. The seating confirming means 10 confirms whether or not the work W is seated on the basis of the position of the work W to loader head 16 by the work position detecting means 22.