A backing material that is advantageous in insulation property and can realize a desired acoustic impedance without making the cross-linking and curing reaction of elastomer or resin as a parent material unstable. The backing material is provided on a backside of vibrators for transmitting and/or receiving ultrasonic waves in an ultrasonic probe, and the backing material includes: a parent material containing elastomer or resin and having an insulation property; and composite powder dispersed to fill the parent material, and the composite powder includes powder of a material having a larger acoustic impedance than that of the parent material and an insulation coating for covering a surface of the powder, and the insulation coating contains an oxide of an element of group XIII to group XV except for carbon (C), nitrogen (N), phosphorus (P).