A vibration isolating apparatus employed for mounting, for example, the engine of an automobile includes a tube communicated with a hollow chamber which is expanded and contracted by vibrations generated in the engine. The tube is provided therein with a mass member which has a larger density than that of a fluid sealed inside the hollow chamber. The mass member is movable by means of the circulation of the fluid inside the tube. Accordingly, the mass member encourages the occurrence of resonance of the fluid inside the tube, whereby the vibrations are absorbed by means of the air-column resonance.