To efficiently perform the measurement of a repulsive force and preliminary excitation of a buffer.

A holding device 7 which holds the external thread section 4 of a rod 3 end of the buffer 2, and a shaker 8 which applies vibration to the buffer 2 by reciprocating the holding device 7 are included. The holding device 7 is divided into a first and second jig 9a, 9b, and has a holding jig 9 which releasably holds the external thread section 4 with the internal thread section 6 formed on the inner peripheral surface, and a positioning member 36 which is arranged coaxially with the rod 3 and which performs the positioning of the external thread section 4, with respect to the holding jig 9 by the contact of the end surface of the rod 3, when the external thread section 4 is inserted into the internally threaded hole of the holding jig 9. The repulsive force is measured by applying a load to the rod 3 through the positioning member 36, while the hold by the holding jig 9 is released. The preliminary excitation is performed, by holding the external thread section 4 with the holding jig 9 and applying vibration to the buffer 2, after the positioning member 36 has performed positioning of the external thread section 4, with respect to the holding jig 9.