A particulate sensor including a sensor unit (300) having an ion generation section (611, 361, 322); an electric charge section (612) for electrically charging at least portion of particulates S using ions PI; a capture section (616, 617, 316, 326, 362) for trapping at least portion of the ions PI not used for electrically charging the particulates S; and a sensor ground section (340, 310v, 330v3) connected to the capture section and having a first floating potential corresponding to the amount of the ions PI trapped by the capture section. The sensor unit can detect the amount of the particulates S in the gas on the basis of the electric potential of the sensor ground section. The sensor ground section is covered with insulating ceramic at that outer portion of the sensor unit which comes into contact with the gas.