an apparatus for detecting the shake of an image of an object , having first and second photosensor arrays for detecting an image of an object in two different directions , a signal processor for processing output signals from the first and second photosensor arrays and for producing a focusing control signal of an objective lens , a memory circuit for storing an output signal from the first photosensor array , and a discrimination circuit for discriminating the shake of the object in accordance with the signal stored in the memory circuit and a signal from the first photosensor array produced subsequent to this signal .