A misfire detecting device for an engine is provided, which includes a processor configured to execute a cylinder operation controlling module to switch an engine operation mode from an all-cylinder operation to a reduced-cylinder operation in which operation of one or some of cylinders are suspended, when an execution condition of the reduced-cylinder operation is satisfied, a misfire detecting module to detect a possibility of misfire occurrence based on an angular speed variation of the engine, and a centrifugal damping part configured to reduce vibration caused by the engine. When a possible misfire state is detected by the misfire detecting module during the reduced-cylinder operation, the cylinder operation controlling module executes an operating-cylinder increase control in which the number of operating cylinders is increased. When the possible misfire state is continuously detected after the operating-cylinder increase control, the misfire detecting module detects the engine misfire.