A pump (1, 1A, 1B, 1C, 1D, 1E, 1F, 1G) 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 (9, 9B) 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 (19, 19A, 19B, 19D, 19E, 19F) 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 (19, 19A, 19B, 19D, 19E, 19F) 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 (31a, 31b) of the top plate and the second main surface of the vibrating plate face each other; and the support portion (9, 9B) has a beam shape that extends along an outer peripheral edge of the vibrating plate; wherein the support portion (9, 9A) 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 (9, 9B) 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 (19, 19A, 19B, 19D, 19E, 19F) 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 (19, 19A, 19B, 19D, 19E, 19F) 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 (31a, 31b) of the top plate and the second main surface of the vibrating plate face each other; and the support portion (9, 9B) has a beam shape that extends along an outer peripheral edge of the vibrating plate; wherein the support portion (9, 9A) 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