An apparatus for detecting movement direction of object, includes a converging lens, an image sensor and an image processor. The converging lens has an axial chromatic aberration between a first and a second rays in different wavelengths. The image sensor is for receiving and converting the first and second rays into first and second electronic image signals associated with the object. The image processor is configured for analyzing whether the object is closer to an object plane associated with the first ray or closer to an object plane associated with the second ray when the object moves to different positions, and determining the movement direction of the object based on the analyzed positions of the object relative to the object plane associated with the first ray and the object plane associated with the second ray.