To avoid that control diverges due to a change in a transfer characteristic of a transmission system due to a temp. change by detecting a temp. in the transmission system and updating a renewal relation according to the detected temp.

A temp. detection value (t) from a temp. sensor is read in (step 131). A temp. range containing the read in temp. detection value (t) is specified referring to a correspondent table beforehand set and stored in a prescribed storage area (step 132). The temp. range specified this time is compared with the temp. range specified the last time beforehand preserved in the prescribed storage area, and whether or not the temp. range is changed is decided (step 133). When the temp. range is changed, values of a convergent coefficient αand a divergent suppression coefficient β are replaced to the values of newly specified convergent coefficient a and divergent suppression coefficient β referring to the correspondent table (step 134). A filter coefficient is set based on the renewal relation that these coefficients α, β are revised, and vibration reduction control is performed based on the coefficients.