A diesel particulate filter failure detection method for detecting a failure in a diesel particulate filter that is arranged in an exhaust pipe guiding exhaust gas from an internal combustion engine to the atmosphere, the diesel particulate filter failure detection method comprising: calculating a theoretical deposited amount of a particulate matter deposited on the diesel particulate filter from an operating state of the internal combustion engine; and measuring an actual deposited amount of the particulate matter on the diesel particulate filter; characterized in that the actual deposited amount is measured based on an electrical capacitance of an electrical capacitance type particulate matter sensor configured by two electrodes disposed in the diesel particulate filter, wherein the diesel particulate filter failure detection method further comprises: calculating a difference between the theoretical deposited amount and the actual deposited amount or calculating a difference between an increase rate of the theoretical deposited amount and an increase rate of the actual deposited amount when the actual deposited amount is smaller than the theoretical deposited amount, and when the difference between the theoretical deposited amount and the actual deposited amount is equal to or greater than a predetermined value or when the difference in the increase rate is equal to or greater than a predetermined value, determining that the diesel particulate filter has a failure; and calculating the difference between the actual deposited amount and the theoretical deposited amount or calculating the difference between the increase rate of the actual deposited amount and the increase rate of the theoretical deposited amount when the actual deposited amount is greater than the theoretical deposited amount, and when the difference between the actual deposited amount and the theoretical deposited amount is equal to or greater than the predetermined value or when the difference in the increase rate is equal to or greater than the predetermined value, determining that there is an engine failure. calculating a theoretical deposited amount of a particulate matter deposited on the diesel particulate filter from an operating state of the internal combustion engine; and measuring an actual deposited amount of the particulate matter on the diesel particulate filter; characterized in that the actual deposited amount is measured based on an electrical capacitance of an electrical capacitance type particulate matter sensor configured by two electrodes disposed in the diesel particulate filter, wherein the diesel particulate filter failure detection method further comprises: calculating a difference between the theoretical deposited amount and the actual deposited amount or calculating a difference between an increase rate of the theoretical deposited amount and an increase rate of the actual deposited amount when the actual deposited amount is smaller than the theoretical deposited amount, and when the difference between the theoretical deposited amount and the actual deposited amount is equal to or greater than a predetermined value or when the difference in the increase rate is equal to or greater than a predetermined value, determining that the diesel particulate filter has a failure; and calculating the difference between the actual deposited amount and the theoretical deposited amount or calculating the difference between the increase rate of the actual deposited amount and the increase rate of the theoretical deposited amount when the actual deposited amount is greater than the theoretical deposited amount, and when the difference between the actual deposited amount and the theoretical deposited amount is equal to or greater than the predetermined value or when the difference in the increase rate is equal to or greater than the predetermined value, determining that there is an engine failure. calculating a difference between the theoretical deposited amount and the actual deposited amount or calculating a difference between an increase rate of the theoretical deposited amount and an increase rate of the actual deposited amount when the actual deposited amount is smaller than the theoretical deposited amount, and when the difference between the theoretical deposited amount and the actual deposited amount is equal to or greater than a predetermined value or when the difference in the increase rate is equal to or greater than a predetermined value, determining that the diesel particulate filter has a failure; and calculating the difference between the actual deposited amount and the theoretical deposited amount or calculating the difference between the increase rate of the actual deposited amount and the increase rate of the theoretical deposited amount when the actual deposited amount is greater than the theoretical deposited amount, and when the difference between the actual deposited amount and the theoretical deposited amount is equal to or greater than the predetermined value or when the difference in the increase rate is equal to or greater than the predetermined value, determining that there is an engine failure.