FAULT DETECTION DEVICE AND FAULT DETECTION METHOD

A fault detection device includes a wastegate valve (23), a control unit (31), a working gas amount computation section (35), and a determination section (38). The control unit (31) obtains a rotational speed (NE) of an engine (10), a boost pressure (Pb), and an intake air i temperature (Tin). The working gas amount computation section (35) computes a computed value (Gc) of a mass flow rate of working gas in the engine (10) by using the rotational speed (NE), the boost pressure (Pb), and the intake air temperature (Tin). The determination section (38) determines that the wastegate valve (38) has a fault when the computed value (Gc) is not a normal value (Gs).