To provide a water hammering preventing unit capable of surely preventing the generation of water hammering by absorbing the high-speed condensate flow for buffering at a bend part of a steam piping.

A main body 3 is provided with an inlet 1 and an outlet 2 through a bend part 6. A buffer 7 is fitted to the bend part 6 in a position opposite to the inlet 1. The buffer 7 is formed of a plate spring fitting member 17 and resistant plates 23, 24, 25, 26 made of a reversing plate spring. The high-speed condensate flow flowing-in from the inlet 1 is buffered by standing the resistant plates 23, 24, 25, 26 of the buffer 7, and the generation of water hammering is thereby prevented.