To provide a misfire detecting device for an internal combustion engine capable of accurately detecting misfire in distinction from irregular combustion.

A first correction rotation speed OMGMA(i)is calculated by a 720 degree filter process, a second correction rotation speed OMGMB(i) is calculated by a 1440 degree filter process, and first and second determination parameters MFPARAMA(k), MFPARAMB(k) are calculated by using the first and second correction rotation speeds OMGMA(i), OMGMB(i). When it is determined that possibility of a misfire is high by the first determination parameter MFPARAMA(k), and the engine 1 is in warm-up idling state right after a cold start, misfire determination is carried out by the second determination parameter MFPARAMB(k). If the engine 1 is not in the warm-up idling state, a determination result by the first determination parameter MFPARAMA(k) is adopted.