An activated gas generation apparatus comprising: a substrate accommodating part for accommodating a substrate to be treated; an activated gas generating electrode group including first and second electrode constituent parts (1A, 2A) the second electrode constituent part having a plurality of gas spray holes discretely formed in said second electrode constituent part, the activated gas generating electrode group being configured to spray an activated gas obtained by utilizing a discharge phenomenon from a source gas from the plurality of gas spray holes, each of said plurality of gas spray holes is formed in a circular opening cross-sectional shape with a first diameter in plan view and is configured as a first restricting cylinder; and said first diameter being set so that a pressure difference between a primary pressure before passing through said gas spray holes and a secondary pressure after passing through said gas spray holes is equal to or higher than a predetermined pressure ratio; a nozzle constituent part including a plurality of nozzle parts provided to correspond to said plurality of gas spray holes of said activated gas generating electrode group one-on-one, each of the nozzle parts causing the activated gas sprayed from each of said plurality of gas spray holes to pass therethrough, to obtain a nozzle passing activated gas; and a gas jet flow straightener (70, 70B, 70C)) including an inlet part (711, 711B, 711C) configured to receive the plurality of nozzle passing activated gases passing through said nozzle constituent part, an outlet part (710, 710B, 710C) configured to inject the flow-straightened activated gas toward said substrate to be treated, and a gas flow-straightening passage (71, 71B, 71C), wherein a flow-straightening action causes said plurality of nozzle passing activated gases to pass through the gas flow-straightening passage (71, 71B, 71C), wherein each of said plurality of nozzle parts includes a second restricting cylinder (14, 14B) formed in a circular opening cross-sectional shape with a second diameter in plan view and configured to supply the activated gas supplied from said first restricting cylinder toward said gas jet flow straightener (70, 70B, 70C); said second diameter is set to be greater than said first diameter, and said nozzle passing activated gases are cylindrical gas jets; and said gas flow-straightening passage (71, 71B, 71C) is formed so that an outlet opening area of said outlet part (710, 710B, 710C) is set to be narrower than an inlet opening area of said inlet part (711, 711B, 711C), and cylindrical gas jets of said plurality of nozzle passing activated gases are converted into said linear flow-straightened activated gas along a predetermined direction by said flow-straightening action. a substrate accommodating part for accommodating a substrate to be treated; an activated gas generating electrode group including first and second electrode constituent parts (1A, 2A) the second electrode constituent part having a plurality of gas spray holes discretely formed in said second electrode constituent part, the activated gas generating electrode group being configured to spray an activated gas obtained by utilizing a discharge phenomenon from a source gas from the plurality of gas spray holes, each of said plurality of gas spray holes is formed in a circular opening cross-sectional shape with a first diameter in plan view and is configured as a first restricting cylinder; and said first diameter being set so that a pressure difference between a primary pressure before passing through said gas spray holes and a secondary pressure after passing through said gas spray holes is equal to or higher than a predetermined pressure ratio; a nozzle constituent part including a plurality of nozzle parts provided to correspond to said plurality of gas spray holes of said activated gas generating electrode group one-on-one, each of the nozzle parts causing the activated gas sprayed from each of said plurality of gas spray holes to pass therethrough, to obtain a nozzle passing activated gas; and a gas jet flow straightener (70, 70B, 70C)) including an inlet part (711, 711B, 711C) configured to receive the plurality of nozzle passing activated gases passing through said nozzle constituent part, an outlet part (710, 710B, 710C) configured to inject the flow-straightened activated gas toward said substrate to be treated, and a gas flow-straightening passage (71, 71B, 71C), wherein a flow-straightening action causes said plurality of nozzle passing activated gases to pass through the gas flow-straightening passage (71, 71B, 71C), wherein each of said plurality of nozzle parts includes a second restricting cylinder (14, 14B) formed in a circular opening cross-sectional shape with a second diameter in plan view and configured to supply the activated gas supplied from said first restricting cylinder toward said gas jet flow straightener (70, 70B, 70C); said second diameter is set to be greater than said first diameter, and said nozzle passing activated gases are cylindrical gas jets; and said gas flow-straightening passage (71, 71B, 71C) is formed so that an outlet opening area of said outlet part (710, 710B, 710C) is set to be narrower than an inlet opening area of said inlet part (711, 711B, 711C), and cylindrical gas jets of said plurality of nozzle passing activated gases are converted into said linear flow-straightened activated gas along a predetermined direction by said flow-straightening action.