PURPOSE: To prevent erroneous calculation of a control parameter so as to realize high accuracy.

CONSTITUTION: An internal combustion engine control device is provided with a normal condition judging means 36 for judging normal condition of an internal combustion engine and a periodical ratio calculating means 37 for finding out a normal condition periodical ratio αo in normal condition of the internal combustion engine while calculating a periodical ratio α between the first zone period T70 and the second zone period T110 of a reference position signal SGT. A control parameter calculating means 32A includes a prediction period calculating means 33A for calculating a prediction period Tex' on the basis of the first zone period, the second zone period, the period ratio and the normal condition period ratio, and a correcting means 35 for correcting a control parameter Ta' on the basis of the prediction period, and a reference position error is found out as offset on the basis of the normal condition period ratio. And the control parameter is corrected so as to offset against the reference position error.