To accurately inspect the caulking strength of a roller shaft in a valve system component with an inexpensive tool for a short time.

A movable tool 13 and a fixed tool 14 are held in a holder 12. A main body 3 of a swing arm 2 is set inside the holder 12, and a fastening bolt 24 is fastened. Press-in parts 20 and 21 of the tools 13 and 14 are broken into both end surfaces of the roller shaft 6 to form a groove traces inside a caulking groove 8. The arm body 3 is fixed to a vice in the state where the tools 13 and 14 are retained in the groove traces. A fixing bolt 26 is turned with a torque wrench to impart rotation torque to the roller shaft 6 via the fixed tool 14. Based on the measurement value of the rotation torque, the caulking strength of the roller shaft 6 is inspected.