A pump device comprising an actuator support structure, the actuator support structure comprising: a plate-shaped actuator which flexurally vibrates from a centre portion of a principal surface thereof to an outer peripheral portion thereof; a side wall (2, 5A) which surrounds outside of an outer periphery of the actuator; and an elastic support portion which elastically supports the outer periphery of the actuator to the side wall, wherein the elastic support portion includes: a beam portion, having a substantially circular arc shape, which extends in a gap between the actuator and the side wall in a direction along the outer periphery of the actuator; an actuator connection portion which connects the beam portion to the actuator (3, 24); and a side wall connection portion (27, 28) which is provided in a position offset from the actuator connection portion in the direction along the outer periphery of the actuator and connects the beam portion to the side wall; and wherein the side wall (2, 5A) of the actuator support structure is included in a housing of the pump device, the housing also including an opposed wall (2, 5C) which is located so as to be adjacent to and opposed to the principal surface of the actuator; and wherein the opposed wall (2, 5C) is provided with a flow path hole in a centre of a region facing the actuator or in the vicinity of the centre, through which flow path hole a fluid flows in. a plate-shaped actuator which flexurally vibrates from a centre portion of a principal surface thereof to an outer peripheral portion thereof; a side wall (2, 5A) which surrounds outside of an outer periphery of the actuator; and an elastic support portion which elastically supports the outer periphery of the actuator to the side wall, wherein the elastic support portion includes: a beam portion, having a substantially circular arc shape, which extends in a gap between the actuator and the side wall in a direction along the outer periphery of the actuator; an actuator connection portion which connects the beam portion to the actuator (3, 24); and a side wall connection portion (27, 28) which is provided in a position offset from the actuator connection portion in the direction along the outer periphery of the actuator and connects the beam portion to the side wall; and a beam portion, having a substantially circular arc shape, which extends in a gap between the actuator and the side wall in a direction along the outer periphery of the actuator; an actuator connection portion which connects the beam portion to the actuator (3, 24); and a side wall connection portion (27, 28) which is provided in a position offset from the actuator connection portion in the direction along the outer periphery of the actuator and connects the beam portion to the side wall; and wherein the side wall (2, 5A) of the actuator support structure is included in a housing of the pump device, the housing also including an opposed wall (2, 5C) which is located so as to be adjacent to and opposed to the principal surface of the actuator; and wherein the opposed wall (2, 5C) is provided with a flow path hole in a centre of a region facing the actuator or in the vicinity of the centre, through which flow path hole a fluid flows in.