PROBLEM TO BE SOLVED: To maintain and recover the uniformity of the viscosity and specific gravity and optimum damping value of slurry introduced into a water tank. SOLUTION: In the tuning liquid damper 1, the inside of a sloshing tank 2 is filled with slurry 3 while an agitator 4 agitating slurry 3 in the tank is installed. The agitator 4 consists of a piping 7 for circulation, in which a suction port 5 and a discharge opening 6 are arranged near the bottom section and level of the sloshing tank 2 respectively, a pump 8 for circulation force-feeding slurry in the pipe, and a power device 10 connected to an electric motor 9 incorporated into the pump 8 for circulation. The power device 10 has a control section 11 connected to an external power supply source, and the control section 11 supplies the electric motor 9 with power from the external power supply source at the time of agitation while supplying a battery 12 with power and charging the battery 12 at a normal time. The control section 11 can program time intervals, a time, etc., feeding the electric motor 9 with power.