An imaging device includes a processor including hardware. The processor is configured to implement controlling a focus position of an objective optical system configured to form an image of a subject on an image sensor, acquiring L×N images per second captured by the image sensor, and combining acquired M images into one extended depth of field image to extend a depth of field, and outputting L extended depth of field images per second. The processor sets one of the M images as a reference image, performs positioning of the other image or images of the M images with respect to the reference image, and combines the thus positioned M images into the one extended depth of field image.