A particulate sensor (1; 1A) having a detection section (10; 10A) attached to a gas flow pipe and adapted to detect an amount of particulates contained in a gas under measurement flowing within the gas flow pipe, wherein the detection section (10; 10A) includes: a space forming portion (12; 12A) configured such that, in a state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, the space forming portion (12; 12A) projects into the gas flow pipe and forms an internal space, the space forming portion (12; 12A) having an introduction port for introducing the gas under measurement into the internal space and a discharge port for discharging from the internal space the gas introduced through the introduction port, and an ion source (15; 15A) for producing ions within the internal space by gaseous discharge; wherein the detection section (10; 10A) further includes a capturing electrode for capturing floating ions which are a portion of the ions and have not adhered to the particulates through mixing with the introduced gas; characterized in that the space forming portion (12; 12A) is configured such that the gas under measurement is introduced into and discharged from the internal space without the assistance of a compressed air source, and the space forming portion (12; 12A) is configured such that, through utilization of a negative pressure produced in the discharge port by the gas under measurement flowing within the gas flow pipe, the introduced gas is discharged from the internal space through the discharge port, the gas under measurement is introduced into the internal space through the introduction port, and the introduced gas is mixed with the ions produced by the ion source (15; 15A); and the space forming portion (12; 12A) forms the capturing electrode, wherein the space forming portion (12; 12A) is configured such that the discharge port has an opening at a distal end of the space forming portion (12; 12A) and the introduction port has an opening on an outer circumferential surface thereof at a position located on a proximal end side in relation to the discharge port, and in the state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, an axial line of the space forming portion (12; 12A) extends within the gas flow pipe in a direction intersecting with a pipe axial line which is an axial line of the gas flow pipe, wherein the space forming portion (12; 12A) has a taper portion which is tapered off, the discharge port is located at a distal end of the taper portion, and, in the state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, a facing direction of the opening of the discharge port is orthogonal to the pipe axial line. a space forming portion (12; 12A) configured such that, in a state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, the space forming portion (12; 12A) projects into the gas flow pipe and forms an internal space, the space forming portion (12; 12A) having an introduction port for introducing the gas under measurement into the internal space and a discharge port for discharging from the internal space the gas introduced through the introduction port, and an ion source (15; 15A) for producing ions within the internal space by gaseous discharge; wherein the detection section (10; 10A) further includes a capturing electrode for capturing floating ions which are a portion of the ions and have not adhered to the particulates through mixing with the introduced gas; characterized in that the space forming portion (12; 12A) is configured such that the gas under measurement is introduced into and discharged from the internal space without the assistance of a compressed air source, and the space forming portion (12; 12A) is configured such that, through utilization of a negative pressure produced in the discharge port by the gas under measurement flowing within the gas flow pipe, the introduced gas is discharged from the internal space through the discharge port, the gas under measurement is introduced into the internal space through the introduction port, and the introduced gas is mixed with the ions produced by the ion source (15; 15A); and the space forming portion (12; 12A) forms the capturing electrode, wherein the space forming portion (12; 12A) is configured such that the discharge port has an opening at a distal end of the space forming portion (12; 12A) and the introduction port has an opening on an outer circumferential surface thereof at a position located on a proximal end side in relation to the discharge port, and in the state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, an axial line of the space forming portion (12; 12A) extends within the gas flow pipe in a direction intersecting with a pipe axial line which is an axial line of the gas flow pipe, wherein the space forming portion (12; 12A) has a taper portion which is tapered off, the discharge port is located at a distal end of the taper portion, and, in the state in which the particulate sensor (1; 1A) is attached to the gas flow pipe, a facing direction of the opening of the discharge port is orthogonal to the pipe axial line.