A particulate matter accumulation amount detection apparatus includes a filter pressure loss detecting section, an incombustible component amount estimating section, an incombustible component accumulation state estimating section, and a particulate accumulation amount detecting section. The filter pressure loss detecting section is configured to detect an upstream-downstream differential pressure of an exhaust gas purification filter having a plurality of substrate walls. The incombustible component amount estimating section is configured to estimate an amount of an incombustible component. The incombustible component accumulation state estimating section is configured to estimate an accumulation state of the incombustible component on the substrate walls based on the engine operating state and the amount of the incombustible component. The particulate accumulation amount detecting section is configured to detect an amount of the particulate matter accumulated in the exhaust gas purification filter based on the upstream-downstream differential pressure and the accumulation state of the incombustible component.