To supply a product of highly complete round stably by measuring a machined surface while maintaining a machining attitude in a NC lathe.

This device has a drive means for rotating a work 10 around a rotary shaft C and a table 11 which can approach and separate freely the work 10 in the rotary shaft C direction. A tool 15 which can form a bent recessed surface 10a to the work 10 and a measuring tool 16 which can measure a machined surface while keeping the processed posture of the work 10 are provided on the table 11. The tool 15 and measuring tool 16 are provided so as to be turned by the sectional radius Rs of the bent recessed surface 10a and arranged turnably on the surface passing the rotary shaft C with an equal distance from the rotary shaft C of the work 10. After creating the bent recessed surface 10a on the work 10 by the tool 15, a shape is checked by the measuring tool 16 without removing the work 10 from a main spindle 9. Therefore, the bent recessed surface 10a can be measured while maintaining the machining attitude of the work 10 and the accuracy of the shape check of the bent recessed surface 10a can be increased.