To provide a carbon fiber functioning as a reinforcing material having good dispersibility in, stuck properties to and adhesion to a matrix material when being compounded with the matrix material to provide a composite; and to provide a method for producing the carbon fiber.

The carbon fiber 2 which has a fiber cross section cut by an arbitrary cutting face passing the fiber axis, having both edge shapes in the width direction formed into a wave shape repeating bending, and further having 1.5-2.3 μm interval d between the mountains 4 and 4 of the wave shape, and 0.3-0.5 μm difference in heights of the mountains 4 and the valleys 6 of the wave shape is produced by treating a precursor having pulse-shaped unevenness along the fiber axis in oxidation atmosphere at 240-250°C at 1.00-1.10 draw ratio, further treating the treated precursor in an inert atmosphere at 300-600°C at 1.02-1.09 draw ratio, and treating the treated product again in an inert atmosphere at 600-1,500°C at 0.95-0.98 draw ratio.