The present invention provides a plasma reactor which can suppress deactivation of components (active components) activated by plasma when causing exhaust gas to flow through a plasma generating space to ensure efficient reaction between the active components and particulate matter, whereby the particulate matter can be efficiently purified via reaction. The plasma reactor includes a plasma reactor main body 1, a positive electrode 11 disposed on an inlet side 2 of the plasma reactor main body 1, a conductive honeycomb filter 21 disposed so that a filter inlet side 22 faces an outlet side 3 of the plasma reactor main body 1, and a pulse power supply 31 which is connected with the positive electrode 11 and the honeycomb filter 21 and is capable of applying a pulse voltage between the positive electrode 11 and the honeycomb filter 21 as plasma generating electrodes to generate plasma.