A pump comprising: a vibrating plate having a piezoelectric body connected to a first main surface thereof; a cover including a top plate that faces a second main surface of the vibrating plate , which is on the opposite side from the first main surface , and that has an opening part , and a side wall that is connected to an outer peripheral portion of the top plate so as to surround a space between the top plate and the vibrating plate ; a support portion that is connected to the side wall and supports an outer periphery of the vibrating plate ; an opening that is formed between the side wall and the vibrating plate ; characterized in that the pump further comprises a protrusion that is provided on any one out of the top plate , the side wall , and the vibrating plate so as to protrude into the space; wherein the protrusion is provided between the opening part of the top plate and the side wall in a cross section viewed in a direction perpendicular to a direction in which a main surface of the top plate and the second main surface of the vibrating plate face each other; and the support portion has a beam shape that extends along an outer peripheral edge of the vibrating plate ; wherein the support portion includes a beam portion , a first connecting portion that connects the vibrating plate and the beam portion to each other, and a second connecting portion that connects the side wall and the beam portion to each other, and a plurality, namely, three or more of the support portions are provided and the support portions are provided so as to be spaced apart from each other, and wherein a valve is provided outside the opening part of the top plate in a space between the vibrating plate and the top plate , the valve has a ring-like shape. a vibrating plate having a piezoelectric body connected to a first main surface thereof; a cover including a top plate that faces a second main surface of the vibrating plate , which is on the opposite side from the first main surface , and that has an opening part , and a side wall that is connected to an outer peripheral portion of the top plate so as to surround a space between the top plate and the vibrating plate ; a support portion that is connected to the side wall and supports an outer periphery of the vibrating plate ; an opening that is formed between the side wall and the vibrating plate ; a protrusion that is provided on any one out of the top plate , the side wall , and the vibrating plate so as to protrude into the space; wherein the protrusion is provided between the opening part of the top plate and the side wall in a cross section viewed in a direction perpendicular to a direction in which a main surface of the top plate and the second main surface of the vibrating plate face each other; and the support portion has a beam shape that extends along an outer peripheral edge of the vibrating plate ; wherein the support portion includes a beam portion , a first connecting portion that connects the vibrating plate and the beam portion to each other, and a second connecting portion that connects the side wall and the beam portion to each other, and a plurality, namely, three or more of the support portions are provided and the support portions are provided so as to be spaced apart from each other, and wherein <EOS>