An ultrasonic generator comprising: a first case member; a second case member that is secured to the first case member, the first and second case member together defining a case having an interior and an interior wall, the case interior forming an accomodation space for housing an ultrasonic generating element; an ultrasonic generating element accommodated in the accommodation space; and a first supporting member that is provided at the first case member, the first supporting member supporting the ultrasonic generating element so that a space is formed between a bottom surface of the ultrasonic generating element and a top surface of the first case member, and so that the periphery of the ultrasonic generating element is spaced away from the interior wall of the case wherein a sound-wave emission hole (12a to 12d) from which an ultrasonic wave is emitted is provided in one of the first case member and the second case member, and a sound wave generated by the ultrasonic generating element moves to the sound-wave emission hole (12a to 12d) along a first acoustic path from a sound pressure generation center point of the ultrasonic generating element, via the space formed between the bottom surface of the ultrasonic generating element and the top surface of the first case member to the sound emission hole (12a to 12d) wherein the first supporting member comprises at least two opposing portions arranged at the periphery of the ultrasonic generating element between the bottom surface of the ultrasonic generating element and the top surface of the first case member and spaced from the interior wall of the case, the two opposing portions are shaped such that in the first acoustic path a transverse section of the acoustic path has a portion that becomes smaller than another portion thereof is provided and such that the sound pressure at the sound-wave emission hole is increased. a first case member; a second case member that is secured to the first case member, the first and second case member together defining a case having an interior and an interior wall, the case interior forming an accomodation space for housing an ultrasonic generating element; an ultrasonic generating element accommodated in the accommodation space; and a first supporting member that is provided at the first case member, the first supporting member supporting the ultrasonic generating element so that a space is formed between a bottom surface of the ultrasonic generating element and a top surface of the first case member, and so that the periphery of the ultrasonic generating element is spaced away from the interior wall of the case wherein a sound-wave emission hole (12a to 12d) from which an ultrasonic wave is emitted is provided in one of the first case member and the second case member, and a sound wave generated by the ultrasonic generating element moves to the sound-wave emission hole (12a to 12d) along a first acoustic path from a sound pressure generation center point of the ultrasonic generating element, via the space formed between the bottom surface of the ultrasonic generating element and the top surface of the first case member to the sound emission hole (12a to 12d) wherein the first supporting member comprises at least two opposing portions arranged at the periphery of the ultrasonic generating element between the bottom surface of the ultrasonic generating element and the top surface of the first case member and spaced from the interior wall of the case, the two opposing portions are shaped such that in the first acoustic path a transverse section of the acoustic path has a portion that becomes smaller than another portion thereof is provided and such that the sound pressure at the sound-wave emission hole is increased.