An object of the present invention is to elongate service life of a sensor unit adapted to detect the amount of particulates in gas which contains particulates, through utilization of corona discharge. The sensor unit 300 includes an ion generation section (611, 361, 322) for generating ions; an electric charge section (612) for electrically charging at least portion of the particulates S in the gas which contains the particulates S, by use of the 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 300 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
