The present invention makes it possible to prevent an excessive exhaust temperature increase when HC is supplied to an oxidation catalyst, and to effectively suppress thermal degradation of an SCR catalyst. The invention is provided with: a first oxidation catalyst (31) that is provided in an exhaust system of an internal combustion engine (10); a second oxidation catalyst (32) that is provided in the exhaust system downstream of the first oxidation catalyst (31); a selective reduction catalyst (41) that is provided in the exhaust system downstream of the second oxidation catalyst (32) and reduces and purifies NOx in the exhaust using NH3 generated from urea water as a reducing agent; a third exhaust temperature sensor (53) that detects the temperature of the exhaust flowing into the selective reduction catalyst (41); a temperature increase control unit (62) that periodically implements temperature increase control in which HC is supplied to the first oxidation catalyst (31) to increase the exhaust temperatur
