An ultrasonic sensing device includes a support body and an ultrasonic sensor. The support body includes an accommodating space, and a positioning space at a center of the accommodating space. The ultrasonic sensor includes a body portion in the positioning space, at least one sensing channel portion extending from the body portion and in the accommodating space, at least one piezoelectric unit at one end surface of the sensing channel portion, and a second channel passing through the body portion. An inner diameter of the positioning space is greater than an inner diameter of the accommodating space, and an outer diameter of the sensing channel portion is smaller than the inner diameter of the accommodating space. Thus, a gap is formed between the sensing channel portion and the accommodating space, and the piezoelectric unit is located outside the accommodating space to come into contact with an exterior.