Ultrasonic projection device

An ultrasonic projection device for projecting ultrasonic waves, comprising:

• a first block body;
• a second block body;
• and
• a vibration generation section sandwiched between the first block body and the second block body,
• wherein a vibration plate is provided at one end on a side where the first block body is present as viewed in a direction of arrangement of the first block body, the second block body, and the vibration generation section,
• wherein a dimension in the direction of arrangement from the one end to the other end on a side where the second block body is present approximately coincides with half of the wavelength of vibration generated by the vibration generation section, and
• wherein a connection portion is provided between the vibration plate and a base portion which supports the vibration plate, the connection portion having a groove with a smooth inner wall surface which connects the vibration plate and the base portion.