The present invention provides a floor support member and floor construction. A mass body (40) shows a cylinder shape having a dent (42) in a central part of the lower surface (40A) under a setup status. The dent (42) is a cylinder shape with a coaxial line with the central axis of the mass body (40). Under the setup status, a buffering base frame (26) is arranged in the dent (42), and the lower surface (40A) of the mass body (40) is configured at a position of a side part of the dent (42) for coating a buffer rubber (18).