To provide a damper mass connected to a vibrator through a spring and light and easy to handle in transportation.

The damper mass includes: a hollow mass body 5 provided with a filling opening 51 opened in the top surface; and a seal cap 6 for sealing the filling opening 51 while filling liquid inside the mass body 5 through the filling opening 51. The seal cap 6 has a cap body 61 to be screwed into the filling opening 51 and a protrusion 63 provided in a lower end of the cap body 61 so as to be inserted into the mass body 5 through the filling opening 51. A specific gravity of the protrusion 63 is made different from the specific gravity of the liquid to be filled in the mass body 5, and several kinds of seal caps 6 having the protrusions 63 of different volumes can be exchangeably fit on the filling opening 51. Mass of the damper mass is finely adjusted by exchanging the seal cap 6.