To provide a muting device for a muting piano which can surely stop a hammer from striking strings even when a stopper abuts against a hammer shank while the hammer is close to strings with a relatively simple constitution without changing the timing of the separation of a jack.

The muting device for the muting piano can be switched between a normal musical performance wherein the hammer 2 which rotates as a key is pressed strikes the strings 18 in an inertial motion state wherein the jack 10 is separated and a muted musical performance wherein the strings 18 are stopped from being hit and is equipped with the stopper 16 that the hammer shank 5 abuts against after the jack 10 is separated and a bending moment imparting member 20 which is fitted to the hammer shank 5 and imparts bending moment for bending the hammer shank in the direction wherein the hammer 2 is put away from the strings 18 when the stopper 16 abuts to stop the hammer 2 from striking the strings.