It is an object to provide a tide apparatus comprising a storage tank connected to a underground pit for normally storing water of a constant amount, a connecting pipe for connecting between the underground pit and the storage tank, and a seismograph releasing apparatus formed on the connecting pipe for sensing a shake in an earthquake and for releasing the water stored in the storage tank into the underground pit, wherein the tide plate can protrude upward from the soil foundation face by operating the seismograph releasing apparatus in an earthquake to make the water stored in the storage tank flow into the underground pit via the connecting pipe.