A misfire detecting apparatus for an internal combustion engine is provided. The engine has an output shaft connected via a torsion element to an input shaft of a transmission mechanism. A transmission rotational speed parameter indicative of a rotational speed of the input shaft is detected. A modified engine rotational speed parameter is calculated by modifying the detected engine rotational speed parameter based on the transmission rotational speed parameter, an engine rotation moment on the input side of the torsion element, and a transmission rotation moment on the output side of the torsion element. An average change amount of the modified rotational speed parameter, and an inertia speed changing component, are calculated. Further, a corrected rotational speed parameter is calculated by correcting the modified rotational speed parameter according to the average change amount and the inertia speed changing component. A relative speed parameter is calculated based on the corrected rotational speed parameter, and a determination parameter is calculated by integrating the relative speed parameter. The misfire determination is performed based on the determination parameter.