Inspection system of particulate filter regeneration system

An electronic control unit (6) of a diesel engine controls an operating state of the engine to a first operating state, in which particulate matters are easily generated, when inspection of a particulate filter regeneration system is performed. Thus, a particulate matter deposition quantity necessary for the inspection can be obtained in a short period and fuel consumption during the deposition can be reduced. If the particulate matter deposition quantity necessary for the inspection is obtained, regeneration processing of a particulate filter (4) is started. It is determined whether a function of the particulate filter regeneration system is normal based on whether the particulate matters are eliminated by the regeneration processing.