An ultrasound sensor includes a substrate having an opening portion, a diaphragm that blocks the opening portion, and an ultrasound element including a first electrode, a piezoelectric layer, and a second electrode that is laminated on the substrate. The first electrode, piezoelectric layer, and the second electrode are laminated onto the substrate on a side opposite of the opening portion of the diaphragm and overlap to form an active portion. A movable portion of the diaphragm is oscillatable by the active portion and a resonance frequency adjustment portion for adjusting a resonance frequency of the movable portion is provided on a lateral side of the active portion opposing the movable portion.
