An image processing apparatus includes a first storage unit configured to store image data in order of the image data scanned in a main scanning direction, in a first storage device, a transmission unit configured to transmit pixel information of a partial region longer in the main scanning direction of the image data, from the first storage device to a second storage device, and an object discrimination unit configured to reference the pixel information stored in the second storage device and discriminate whether the partial region is an object region based on the pixel information. Thus, according to image processing apparatus, an object can be rapidly detected.