A turbulence generator includes a flat plate member (1) having a plurality of through holes (10a), (10b), and pairs of projecting pieces (11, 12) and (13, 14) projecting respectively from upstream-side edges and downstream-side edges of the through holes (10a), (10b), wherein the pairs of projecting pieces (11, 12) and (13, 14) project alternately to front and back surface sides of the flat plate member (1).