PURPOSE:To accurately detect the amount of ice and ice distribution in an ice heat storage tank of an ice heat storage device. CONSTITUTION:A plurality of detection rods 6, 6... are disposed in an ice heat storage tank of an ice heat storage device for storing fine particle-shaped ice pieces and water so as to extend in a depth direction, and each detection rod 6 is fixed to a frame 5 located at a tank upper part. Further, probes 7, 7... are disposed at a predetermined interval longitudinally of the detection rods 6, and the frame 5 is vertically moved. Electric resistance is detected by rotational movement of the probes 7 to measure the amount of ice. Further, data from each probe is collected to estimate ice amount distribution in an entire heat storage water tank by an estimation part 14.