After an ultrasonic diagnosis apparatus is temporally placed on the receptacle of a docking cart to relieve a weight load, the portable ultrasonic diagnosis apparatus is placed at a predetermined position by sliding the apparatus while guiding it along the shapes of the edges of the receptacle. After the portable ultrasonic diagnosis apparatus is slid on the receptacle and rear foot portions come into contact with the stoppers of the receptacle, the front side of the portable ultrasonic diagnosis apparatus is placed on the receptacle. With this operation, front foot portions are fitted in fitting portions, and the portable ultrasonic diagnosis apparatus is placed at an accurate position on the receptacle. In addition, when an operator places the portable ultrasonic diagnosis apparatus on the receptacle or lifts the portable ultrasonic diagnosis apparatus from the receptacle, the fingers which grasp the apparatus are placed in the recessed portions of the receptacle.