An ejector comprising: a first nozzle to which a working fluid in a liquid phase is supplied; a second nozzle into which a working fluid in a vapor phase is sucked; an atomization mechanism that is disposed at an end of the first nozzle and that atomizes the working fluid in the liquid phase while maintaining the liquid phase; and a mixing space in which the atomized working fluid in the liquid phase generated in the atomization mechanism and the working fluid in the vapor phase sucked into the second nozzle are mixed to generate a merged fluid flow, wherein the atomization mechanism includes: an ejection section which is attached to the end of the first nozzle and which has a plurality of first orifices, the orifices extend through the ejection section so as to connect the first nozzle to the mixing space; and a collision plate that is disposed on extended lines of center axial lines of the orifices, wherein the collision plate has a collision surface that is inclined with respect to the center axial lines of the orifices, characterized in that, when the collision plate is orthographically projected onto a projection plane, at least one point on a contour of the collision surface is disposed closer to a reference point than a second reference line in a projection of the collision plate, where the reference point is an intersection of a single extended line of the center axial line of a single orifice with the collision surface, a reference plane is a plane that includes the center axial line of a single orifice and that perpendicularly intersects with the collision surface, a collision end point is an intersection of the reference plane with the contour of the collision surface, a first reference line is a line segment that connects the reference point with the collision end point, the second reference line is a line that includes the collision end point and that is perpendicular to the first reference line, and the projection plane is a plane that includes the first reference line and that is perpendicular to the reference plane. a first nozzle to which a working fluid in a liquid phase is supplied; a second nozzle into which a working fluid in a vapor phase is sucked; an atomization mechanism that is disposed at an end of the first nozzle and that atomizes the working fluid in the liquid phase while maintaining the liquid phase; and a mixing space in which the atomized working fluid in the liquid phase generated in the atomization mechanism and the working fluid in the vapor phase sucked into the second nozzle are mixed to generate a merged fluid flow, wherein the atomization mechanism includes: an ejection section which is attached to the end of the first nozzle and which has a plurality of first orifices, the orifices extend through the ejection section so as to connect the first nozzle to the mixing space; and a collision plate that is disposed on extended lines of center axial lines of the orifices, wherein the collision plate has a collision surface that is inclined with respect to the center axial lines of the orifices, characterized in that, when the collision plate is orthographically projected onto a projection plane, at least one point on a contour of the collision surface is disposed closer to a reference point than a second reference line in a projection of the collision plate, where an ejection section which is attached to the end of the first nozzle and which has a plurality of first orifices, the orifices extend through the ejection section so as to connect the first nozzle to the mixing space; and a collision plate that is disposed on extended lines of center axial lines of the orifices, wherein the collision plate has a collision surface that is inclined with respect to the center axial lines of the orifices, characterized in that, when the collision plate is orthographically projected onto a projection plane, at least one point on a contour of the collision surface is disposed closer to a reference point than a second reference line in a projection of the collision plate, where the reference point is an intersection of a single extended line of the center axial line of a single orifice with the collision surface, a reference plane is a plane that includes the center axial line of a single orifice and that perpendicularly intersects with the collision surface, a collision end point is an intersection of the reference plane with the contour of the collision surface, a first reference line is a line segment that connects the reference point with the collision end point, the second reference line is a line that includes the collision end point and that is perpendicular to the first reference line, and the projection plane is a plane that includes the first reference line and that is perpendicular to the reference plane.