To detect a change in electrostatic capacity to determine a fluid material regardless of the type of the fluid material flowing through the inside of a pipe.

This electrostatic capacity sensor is formed by a measuring electrode 33 and a ground electrode 35 which are made of conductive metal foil and wound to circulate around the passage in the pipe through an insulating material 17 and a shielding material 23 covering the outside of the measuring electrode 33 and the ground electrode 35 through an insulating material 21, and capable of detecting the change of electrostatic capacity of the passage in the pipe to precisely and easily determine the fluid material, and precisely keeping the sanitary state.