A digital imaging signal obtained by converting an image data obtained by an imaging element into a digital value for each pixel is inputted to an automatic phase adjusting apparatus, and the automatic phase adjusting apparatus adjusts phases of pulses to be used for imaging based on the inputted digital imaging signal. The automatic phase adjusting apparatus is provided with a brightness level detector for calculating a brightness level of the digital imaging signal for a plurality of pixels in a first pixel region, a variability calculator for calculating a variability value which indicates signal variability of the digital imaging signal for each pixel for a plurality of pixels in a second pixel region, and a timing adjuster for adjusting the phases of the pulses in accordance with calculation results obtained by the brightness level detector and the variability calculator.