1. An ultrasonic diagnostic apparatus comprising: an ultrasonic probe for sending out an ultrasonic wave toward a vital tissue and receiving a reflected wave of the ultrasonic wave that has been reflected from the vital tissue; an image constructing section for constructing an image frame representing a tomographic image of the tissue based on the reflected wave; a display section for displaying the image frame thereon; and a processing section for analyzing an image feature quantity of the image frame and comparing the image feature quantity to a predetermined reference feature quantity, wherein based on a result of the comparison, the apparatus gives a notification that it is time to decide whether its operator wants the image quality of the image frame to be optimized now or not.