A medium conveying apparatus includes a conveying roller to convey a medium, an imaging device to generate an input image acquired by imaging the conveyed medium, and a processor to extract edge pixels from the input image, detect a degree of roundness at a corner of the medium in the input image based on the edge pixels, determine whether the conveyed medium is an ID card based on the degree of roundness, and control the conveying roller based on a result of the determination or outputs the result of the determination.