A capacitive device includes a unit cell including a CMUT, and a transmission/reception plate for impedance matching which is provided above the unit cell via a connection portion, in which a membrane of the CMUT constituting the unit cell is connected to the transmission/reception plate via the connection portion having an area smaller than that of the transmission/reception plate. The area of the transmission/reception plate is desirably larger than the area of a hollow portion of the CMUT.