PURPOSE: To prevent a clearance constituting part or slide part of a pump from the precipitation and deposit of an electrodeposit containing calcium carbonate or the like as a main component from environmental water.

CONSTITUTION: An electric shielding body 7 consisting of an electric conductor is mounted through an insulating material 5 on the outer periphery of a pump part immersed in see water. Also, a lead wire 9 consisting of an electric conductor is mounted on a portion of the electric shielding body 7 and the other end of the lead wire 9 is grounded. Thus, a rotary shaft can be prevented from the increase of sliding resistance caused by the precipitation of an electrodeposit having calcium carbonate or the like as main component on a fine flow path and slide part or the like of the pump so that a serious condition such as the rise of shaft driving power of the pump can be avoided.