A pulsation reducing apparatus is used for an apparatus having a pump for circulating a liquid in a circulating line and a tank for storing the liquid circulating via the pump. The pulsation reducing apparatus includes a supplement tank for reserving the liquid such that a liquid surface height of the supplement tank is higher than that of the tank. The tank is connected to the supplement tank and the empty space portion of the tank is connected to the supplement tank via a gas exhaust line. When the empty space portion of the tank communicates with that of the supplement tank via the gas exhaust line due to a reduction of the liquid in the tank, the gas in the tank is exhausted to the empty space portion of the supplement tank via the gas exhaust line and the liquid in the supplement tank is supplemented into the tank.