An electric power steering control unit that Proportional-Integral -controls a current command value calculated based on at least a steering torque, and drive-controls a motor by means of a control command value which is PI-controlled and assist-controls a steering, comprising: a vibration detecting section to detect a vibration of a vibration suppression target object and to output a vibration signal; a continuation-time judging section to output a continuation signal when said vibration signal continues equal to or more than a predetermined time; and a gain setting section to change a gain of said PI-control based on said continuation signal, characterized in that said vibration detecting section comprises: a band pass filter to extract a predetermined frequency of 5 to 20 Hz of said vibration suppression target object; a sin-wave generating section to generate a sin-wave; a cos-wave generating section to generate a cos-wave; a first multiplying section to multiply said sin-wave with vibration suppression target object signal which is processed in said BPF; a second multiplying section to multiply said vibration suppression target object signal with said cos-wave; a first integrating section to integrate a first multiplied signal from said first multiplying section; a second integrating section to integrate a second multiplied signal from said second multiplying section; a first squaring section to square a first integration signal from said first integrating section; a second squaring section to square a second integration signal from said second integrating section; and an adding section to add a first multiplied signal from said first squaring section and a second multiplied signal from said second squaring section and to output said vibration signal, and a vibration suppression of said vibration suppression target object is performed in a continuation of the predetermined frequency of 5 to 20 Hz of said vibration signal based on an expression of Fourier series for equal to or more than said predetermined time. a vibration detecting section to detect a vibration of a vibration suppression target object and to output a vibration signal; a continuation-time judging section to output a continuation signal when said vibration signal continues equal to or more than a predetermined time; and a gain setting section to change a gain of said PI-control based on said continuation signal, characterized in that said vibration detecting section comprises: a band pass filter to extract a predetermined frequency of 5 to 20 Hz of said vibration suppression target object; a sin-wave generating section to generate a sin-wave; a cos-wave generating section to generate a cos-wave; a first multiplying section to multiply said sin-wave with vibration suppression target object signal which is processed in said BPF; a second multiplying section to multiply said vibration suppression target object signal with said cos-wave; a first integrating section to integrate a first multiplied signal from said first multiplying section; a second integrating section to integrate a second multiplied signal from said second multiplying section; a first squaring section to square a first integration signal from said first integrating section; a second squaring section to square a second integration signal from said second integrating section; and an adding section to add a first multiplied signal from said first squaring section and a second multiplied signal from said second squaring section and to output said vibration signal, and a band pass filter to extract a predetermined frequency of 5 to 20 Hz of said vibration suppression target object; a sin-wave generating section to generate a sin-wave; a cos-wave generating section to generate a cos-wave; a first multiplying section to multiply said sin-wave with vibration suppression target object signal which is processed in said BPF; a second multiplying section to multiply said vibration suppression target object signal with said cos-wave; a first integrating section to integrate a first multiplied signal from said first multiplying section; a second integrating section to integrate a second multiplied signal from said second multiplying section; a first squaring section to square a first integration signal from said first integrating section; a second squaring section to square a second integration signal from said second integrating section; and an adding section to add a first multiplied signal from said first squaring section and a second multiplied signal from said second squaring section and to output said vibration signal, and a vibration suppression of said vibration suppression target object is performed in a continuation of the predetermined frequency of 5 to 20 Hz of said vibration signal based on an expression of Fourier series for equal to or more than said predetermined time.